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Preface

Hitachi Simple Modular Storage Copy-on-Write SnapShot User’s Guide

Document Revision Level

This section provides a history of the revision changes to this document.

•

Safety and Warnings

This document uses the following symbols to draw attention to important 

safety and operational information. The Danger, Electric Shock, and ESD 

symbols are included only in hardware manuals.

•

Intended Audience

This document is intended for users with the following background:
• Background in data processing and understands RAID storage systems 

and their basic functions.

• Familiarity with Hitachi Modular Storage systems.
• Familiarity with operating systems such as the Windows 2000, Windows 

Server 2003 operating system, or UNIX.

Product Version

This document applies to Hitachi Simple Modular Storage 100 microcode 

versions 1810/A and higher.

Release Notes

Make sure to read the Release Notes before enabling and using this product. 

The Release Notes are located on the installation CD. They may contain 

requirements and/or restrictions that are not fully described in this 

document. The Release Notes may also contain updates and/or corrections 

to this document.

Revision

Date

Description

MK-97DF8018-00

October 2007

Initial Release

Symbol

Meaning

Description

•

Tip

Tips provide helpful information, guidelines, or suggestions for 
performing tasks more effectively.

•

Note

Notes emphasize or supplement important points of the main 
text.

•

Caution

Cautions indicate that failure to take a specified action could 
result in damage to the software or hardware.

Summary of Contents for Copy-on Write SnapShot

Page 1: ...i Product Version Document Organization Getting Help Table of Contents FASTFIND LINKS MK 97DF8018 00 Hitachi Simple Modular Storage Copy on Write SnapShot User s Guide ...

Page 2: ...eements All of the features described in this document may not be currently available Refer to the most recent product announcement or contact your local Hitachi Data Systems sales office for information on feature and product availability This document contains the most current information available at the time of publication When new and or revised information becomes available this entire docum...

Page 3: ... Snapshot software using the Storage Navigator 2 graphical user interface This preface includes the following information Document Revision Level Safety and Warnings Product Version Release Notes Referenced Documents Document Conventions Convention for Storage Capacity Values Getting Help Comments Notice The use of the Hitachi Simple Modular Storage 100and all Hitachi Data Systems products is gove...

Page 4: ... 2000 Windows Server 2003 operating system or UNIX Product Version This document applies to Hitachi Simple Modular Storage 100 microcode versions 1810 A and higher Release Notes Make sure to read the Release Notes before enabling and using this product The Release Notes are located on the installation CD They may contain requirements and or restrictions that are not fully described in this documen...

Page 5: ...he Navigator 2 GUI application Chapter Appendix Title Description Chapter 1 SnapShot Overview Provides descriptions of SnapShot components and how they work together Chapter 2 Planning and Design Provides detailed planning and design information Chapter 3 Requirements Provides SnapShot requirements Chapter 4 Enabling and Disabling SnapShot Provides instructions for enabling SnapShot Chapter 5 Conf...

Page 6: ...old Indicates text on a window other than the window title including menus menu options buttons fields and labels Example Click OK Italic Indicates a variable which is a placeholder for actual text provided by the user or system Example copy source file target file Note Angled brackets are also used to indicate variables screen code Indicates text that is displayed on screen or entered by the user...

Page 7: ...ct name model number part number if applicable and serial number System configuration including names of optional features installed host connections and storage configuration such as RAID groups and LUNs Operating system name and revision or service pack number The exact content of any error message s displayed on the host system s The circumstances surrounding the error or failure A detailed des...

Page 8: ...viii Preface Hitachi Simple Modular Storage Copy on Write SnapShot User s Guide ...

Page 9: ...omments vii 1 SnapShot Overview 1 1 Copy on Write SnapShot Software 1 2 Hardware and Software Configuration 1 2 How SnapShot Works 1 3 Volume Pairs P VOLs and V VOLs 1 4 Data Pools 1 6 Differential Management LUs DM LU 1 6 Consistency Group CTG 1 6 SnapShot Interface Storage Navigator Modular 2 1 6 2 Planning and Design 2 1 The Plan and Design Workflow 2 2 Assessing Business Needs 2 2 Establishing...

Page 10: ...inux and LVM Configuration 2 12 Windows Server 2003 Windows 2000 and Dynamic Disk 2 12 3 Requirements 3 1 System Requirements 3 2 Supported Platforms 3 2 4 Enabling and Disabling SnapShot 4 1 Enabling Disabling SnapShot 4 2 5 Configuring SnapShot 5 1 Configuration Workflow 5 2 Assign Volumes for the Data Pool 5 2 Notes on Adding a Data Pool 5 2 Set Up the Virtual Volume V VOL manual method 5 3 6 U...

Page 11: ... Failure Due to a Hardware Failure 8 2 Data Pool Capacity Exceeded 8 3 A Operations Using CLI A 1 Enabling and Disabling SnapShot A 2 Operations for SnapShot Configuration A 3 Setting the POOL A 3 Setting the V VOL A 4 Performing SnapShot CLI Operations A 5 Creating SnapShot Pairs A 5 Updating SnapShot Logical Unit A 6 Restoring V VOL to P VOL A 6 Releasing SnapShot Pairs A 7 Changing Pair Informa...

Page 12: ...xii Contents Hitachi Simple Modular Storage Copy on Write SnapShot User s Guide ...

Page 13: ...dular Storage systems These copies can be used for recovery from logical errors They are identical to the original volume at the point in time they were taken This guide provides instructions for planning and designing configuring and testing and using and monitoring SnapShot In this chapter see Copy on Write SnapShot Software Hardware and Software Configuration How SnapShot Works ...

Page 14: ...riginal data volume The most probable types of target applications for Copy on Write Snapshot are Database copies for decision support database inquiries Non disruptive backups from a Copy on Write Snapshot V VOL Periodic point in time disk copies for rapid restores in the event of a corrupted data volume Hardware and Software Configuration A typical SnapShot hardware configuration includes a Hita...

Page 15: ...e Identify another volume that will contain the copy Associate the primary and secondary volumes Create a snapshot of the primary volume data in the virtual secondary volume Until the new or re synchronized pair is split all data written to the primary volume is also copied to the virtual volume When the pair is split the primary volume continues being updated but the snapshot in the virtual volum...

Page 16: ...ontain copies of the P VOL The P VOL and its V VOL s are located in the same Simple Modular Storage system A V VOL is a mirror image of the P VOL at the time of the snapshot Unlike the P VOL which contains the actual data the V VOL is made up of pointers to the data To maintain the snapshot image of the P VOL as new data is being written to the P VOL SnapShot copies data being replaced to the data...

Page 17: ...SnapShot Overview 1 5 Hitachi Simple Modular Storage Copy on Write SnapShot User s Guide Figure 1 2 V VOL Maintains SnapShot Data ...

Page 18: ...om a host The DM LU is set at the factory at 10 GB User configuration is not required Consistency Group CTG Application data often spans more than one volume With SnapShot it is possible to manage operations spanning multiple volumes as a single group In a consistency group CTG all primary logical volumes are treated as a single entity Managing SnapShot primary volumes as a consistency group allow...

Page 19: ...be used for backup and other uses Creating a backup system that fully supports business continuity is best done when SnapShot is configured to match your business needs This chapter guides you in planning a configuration that meets organization needs and the workload requirements of your host application The Plan and Design Workflow Assessing Business Needs Establishing Data Pool Size Calculating ...

Page 20: ...esign can be implemented These are also addressed in this chapter When you have established your SnapShot system design the system s maximum allowed capacity must be calculated This has to do with how the Storage system manages segments Equally important in the planning process are the ways that various operating systems interact with SnapShot Make sure to review the information at the end of the ...

Page 21: ...l errors in the storage system This would result in snapshots of bad data How long does it take to notice and correct such logical errors The time span for snapshots should provide ample time to locate and correct logical errors in the storage system When longer periods between snapshots are indicated by business needs consider that the longer the period the more data accumulates in the data pool ...

Page 22: ...he amount of time a snapshot is held If snapshot data is used for development purposes development requirements may determine the time the snapshot is held If snapshot data is used for business reports the reporting requirements can determine the backup s lifespan Establishing the Number of V VOLs that Are Required V VOL frequency and lifespan determine the number of V VOLs your system needs per P...

Page 23: ...te workload and data pool size Measuring Workload Data To set up SnapShot you must measure the amount of data that changes in your production system The amount of data written to the primary volume indicates how large the data pool must be Workload data is collected using performance monitoring software on your operating system preferably during the busiest time of month quarter and year The goal ...

Page 24: ...quency established earlier calculate averages over the collection period Most spreadsheet tools have an average function For example If copy frequency is 1 hour then calculate 60 minute rolling averages using the values in 6 10 minute intervals If copy frequency is 4 hours then calculate 240 minute rolling averages using the values in 24 10 minute intervals Figure 2 4 illustrates 60 minute rolling...

Page 25: ...d in C4 It then calculates all the point in time averages and populates the C cells Figure 2 5 illustrates rolling averages graphed over raw measurement data averages Figure 2 5 Rolling Averages Graphed Over Raw Averages 4 Locate the maximum rolling average RA value in the C column Using this peak value and the following formula calculate the cumulative peak data change over the lifespan of a copy...

Page 26: ... 432 000 MB x 1 2 20 percent growth rate for per year 518 400 MB This is the size of the data pool with growth factored for the first year 8 Repeat this step for each year the solution will be in place For example 518 400 MB x 1 2 20 percent growth rate for second year 622 080 MB This is the size of the data pool with growth factored for the second year Rule of Thumb Calculation When measurements ...

Page 27: ... the maximum supported capacity To calculate SnapShot capacity 1 List the size of each P VOL in the Storage system For example P VOL 1 100 GB P VOL 2 50 GB 2 Calculate managed P VOL capacity using the formula ROUNDUP P VOL capacity 15 75 15 75 For example P VOL1 ROUNDUP 100 15 75 7 7 15 75 110 25 GB the managed P VOL Capacity P VOL2 ROUNDUP 50 15 75 4 4 15 75 63 GB the managed P VOL Capacity 3 For...

Page 28: ...rrent copy systems For example 32 000 824 GB 31176 GB 10 From this difference subtract the SnapShot P VOL capacity The difference must be 0 or greater For example 31176 GB 150 GB 31026 GB If your system s maximum capacity exceeds the maximum allowed capacity you can do one or more of the following Change the P VOL size Reduce the number of P VOLs Change the data pool size Reduce the number of V VO...

Page 29: ...er MSCS A host cannot recognize both a P VOL and its V VOL at the same time Map the P VOL and V VOL to separate hosts Veritas Volume Manager VxVM A host cannot recognize both a P VOL and its V VOL at the same time Map the P VOL and V VOL to separate hosts Windows 2000 Multiple V VOLs per P VOL cannot be recognized from the same host Limit host recognition to one V VOL Windows Server 2003 Multiple ...

Page 30: ...and a V VOL as a dynamic disk When using a V VOL with a secondary host insure that the pair status is Split A host cannot recognize both a P VOL and its V VOL at the same time Map the P VOL and V VOL to separate hosts An LU in which two or more dynamic disk volumes coexist cannot be copied Do not use a dynamic disk function for volumes other than a V VOL on the secondary host side When copying hid...

Page 31: ...13 Hitachi Simple Modular Storage Copy on Write SnapShot User s Guide If any one of the dynamic disks is left unhidden a Missing drive occurs When this occurs delete it manually using the diskpart delete command CCI required ...

Page 32: ...User s Guide Copy dynamic disk volumes that consist of two or more LUs only after hiding all LUs from a host When the copy is completed you can have them recognized by a host A dynamic disk cannot be used with a cluster MSCS VCS etc A dynamic disk cannot be used with VxVM and HDLM ...

Page 33: ...3 Requirements 3 1 Hitachi Simple Modular Storage Copy on Write SnapShot User s Guide Requirements This chapter describes minimum operational requirements System Requirements Supported Platforms ...

Page 34: ...ntroller Data Pool Minimum of one per controller maximum of 64 Data Pool Maximum of 64 volumes may be assigned to a pool per controller Data Pool One or more pairs can be assigned to a data pool Command devices Max 128 The command device is required only when CCI is used for SnapShot operation CCI is provided for advanced users only The command device volume size must be greater than or equal to 3...

Page 35: ...chi Simple Modular Storage Copy on Write SnapShot User s Guide Enabling and Disabling SnapShot SnapShot is bundled with the Simple Modular Storage system It must be enabled before using SnapShot can also be disabled Enabling Disabling SnapShot ...

Page 36: ... 3 Select SnapShot in the Licenses list then click the Change Status button at the bottom of the page The Change License screen appears 4 To enable click the Enable Yes check box To disable clear the Enable Yes check box 5 Click OK 6 In the confirmation screen that appears for the enabling and disabling actions click OK The Reboot Array message appears confirming the operation is complete Before b...

Page 37: ...e 7 When ready click the Yes I have read check box at the bottom of the message then click Reboot Array The reboot time displays If the Storage system does not respond after 15 minutes check its condition 8 When rebooting has finished a message appears stating that the restart is successful Click Close ...

Page 38: ...4 4 Enabling and Disabling SnapShot Hitachi Simple Modular Storage Copy on Write SnapShot User s Guide ...

Page 39: ...imple Modular Storage Copy on Write SnapShot User s Guide Configuring SnapShot This chapter describes the steps for setting up SnapShot Configuration Workflow Assign Volumes for the Data Pool Set Up the Virtual Volume V VOL manual method ...

Page 40: ...pool see Data Pools on page 1 6 To create and assign volumes for data pools Advanced users using CLI see Setting the POOL on page A 3 1 In Navigator 2 GUI select the desired array then click the Show Configure Array button 2 From the Replication tree select the Local Replication icon then select the Setup icon The Setup screen displays 3 Select Data Pools View screen instructions by clicking the H...

Page 41: ...and virtual volumes Set up a virtual volumes in Navigator 2 GUI as described in the following procedure To assign volumes as V VOLs Advanced users using CLI see Setting the V VOL on page A 4 1 In Navigator 2 GUI select the desired array then click the Show Configure Array button 2 From the Replication tree select the Local Replication icon then select the Setup icon The Setup screen displays 3 Sel...

Page 42: ...5 4 Configuring SnapShot Hitachi Simple Modular Storage Copy on Write SnapShot User s Guide ...

Page 43: ...flow and processes Details are provided for in system replication along with sample scenarios using SnapShot functionality SnapShot Replication Workflow Back Up Your Volume Create a Pair Update the V VOL Restore the P VOL from the V VOL Use the V VOL for Tape Backup Testing Reports Etc Edit Pairs Data Pool Delete Pairs V VOLs Data Pools Test the Configuration ...

Page 44: ...n page B 2 for primary volume specifications Create a data pool by assigning a volume See Assign Volumes for the Data Pool on page 5 2 Use the create pair procedure which allows more customization described on Page 6 3 This is a more involved method that allows you to set copy pace assign the pair to a group and create a group and automatically split the pair after it is created Preparation consis...

Page 45: ... Local Replication icon The Pairs screen displays 3 Select the Create Pair button The Create Pair screen displays 4 In the Copy Type area click the SnapShot radio button There may be a brief delay while the screen refreshes 5 In the Pair Name box enter a name for the pair 6 In the Primary and Secondary Volume fields select the primary and secondary volumes that you want to pair For SnapShot the se...

Page 46: ...ick OK then click Close on the confirmation screen that appears The pair has been created Update the V VOL Updating the V VOL means to take a new snapshot Two steps are involved when you update the V VOL a resync of the pair and splitting the pair Resyncing means that the P VOL and V VOL are re synchronized This is necessary because the pair became out of sync when the pair was split previously Af...

Page 47: ...oration will complete successfully During the validation stage the host cannot access the P VOL Once validation is complete the P VOL is again available The restoration takes place The actual copying from V VOL to P VOL is performed in the background The P VOL is available for read write from the host during the restoration To restore the P VOL from the V VOL 1 Shut down the host application 2 Un ...

Page 48: ...tion Navigator 2 GUI users please see the resync pair instruction in Update the V VOL on page 6 4 Advanced users using CLI please see the resync pair instruction in Updating SnapShot Logical Unit on page A 6 3 When pair status becomes Paired shut down or quiece quiet the production application if possible 4 Split the pair Doing this insures that the backup will contain the latest mirror image of t...

Page 49: ...r 2 CLI please refer to Storage Navigator Modular 2 Command Line Interface CLI User s Guide for more information 2 In the GUI select Setup then select Data Pool 3 Select the LUN data pool that you want to edit 4 Make changes to editable fields as needed then click OK Delete Pairs V VOLs Data Pools You can delete a pair the V VOL and data pool to free space or when you no longer need them Pair When...

Page 50: ... LU for SnapShot A message appears 5 Click Close The V VOL is deleted To delete a data pool 1 Select the Data Pools icon in the tree view 2 Select a data pool you want to delete in the Data Pool list 3 Click Delete Data Pool 4 A message appears Click Close Test the Configuration You should confirm your system s configuration by closely monitoring pair status and data pool usage See Monitoring Snap...

Page 51: ...provided by SnapShot It is important that data pool capacity is sufficient to handle the differential data from your P VOLs If a data pool should become full the V VOLs associated with it are invalidated and backup data is lost This chapter provides information and instructions for monitoring and maintaining the SnapShot system Monitoring SnapShot Expanding the Data Pool ...

Page 52: ...plays 3 Locate the pair whose status you want to review in the Pair list then review the Status column Click the Refresh Information button to make sure the data is current Statuses and definitions are listed in Table 7 1 Table 7 1 Pair Statuses Pair Status Description Action Simplex Status when the volume has not have been paired or when the pair has been deleted The volume has no SnapShot associ...

Page 53: ...ta Pool When monitoring indicates that the data pool is in danger of filling you can add new volumes to expand its size To expand the data pool capacity The Storage system allows a maximum of 128 volumes for data pools One data pool may consist of up to 64 volumes 1 Split the pair For instructions see Update the V VOL on page 6 4 2 Add a volume or volumes to the data pool Other Methods for Lowerin...

Page 54: ...7 4 Monitoring and Maintenance Hitachi Simple Modular Storage Copy on Write SnapShot User s Guide ...

Page 55: ...te SnapShot User s Guide Troubleshooting Two types of problem can be experienced with a SnapShot system pair failure and data pool capacity exceeded This chapter discusses the causes and provides solutions for these problems Pair Failure Data Pool Capacity Exceeded ...

Page 56: ...the pairs that are using the full data pool 2 Review SnapShot system configuration See Chapter 2 Planning and Design for detailed information on the following Measuring write workload and sizing of the data pool This addresses the amount of data your that accumulates in the data pool and provide calculations for determining the correct size of the data pool Assessing business requirements to estab...

Page 57: ...Guide Data Pool Capacity Exceeded When your data pool capacity is exceeded you must increase the size of the data pool Most likely the POOL FULL condition has caused pair failures as well To address these problems please see Recovering from Pair Failure Due to POOL FULL on page 8 2 ...

Page 58: ...8 4 Troubleshooting Hitachi Simple Modular Storage Copy on Write SnapShot User s Guide ...

Page 59: ...ling configuration and operations Enabling and Disabling SnapShot Operations for SnapShot Configuration Performing SnapShot CLI Operations Sample Back Up Script for Windows CAUTION Storage Navigator 2 CLI is provided for users with significant storage management expertise Improper use of this CLI could void your Hitachi Simple Modular Storage 100 system warranty Please consult with your reseller b...

Page 60: ...leased that is the status of all LUs are SMPL All Data Pools must be deleted All Snapshot Images V VOL must be deleted auopt unit subsystem name option SNAPSHOT st disable Are you sure you want to disable the option y n n y The option has been set successfully In order to complete the setting it is necessary to reboot the subsystem Host will be unable to access the subsystem while restarting Host ...

Page 61: ...e usage rate of 70 the pair in the Split status is changed to the Pool full status An LU with a SAS drive and an LU with a SATA drive cannot coexist in a data pool When using SnapShot with Cache Partition Manager the segment size of the LU belonging to a data pool must be the default size 16 kB or less The following is the procedure for creating a POOL for storing differential data for use by Snap...

Page 62: ...ommand prompt register the subsystem to which you want to set the V VOL then connect to the subsystem 2 Execute the aureplicationvvol command create a V VOL For example aupool unit subsystem name refer poolno 0 Data Pool 0 Data Pool Usage Rate 6 2 0 30 0 GB Threshold 70 Status Normal LUN Capacity RAID Group RAID Level Type Status 100 30 0GB 0 6 9D 2P SAS Normal aupool unit subsystem name rm poolno...

Page 63: ...e assigned to a P VOL and then create a pair Refer to the following example 3 Execute the aureplicationlocal command to verify that the pair has been created Refer to the following example The Snapshot pair is created aureplicationvvol unit subsystem name rm lu 1000 Are you sure you want to delete the SnapShot logical unit 1000 y n n y The SnapShot logical unit has been successfully deleted aurepl...

Page 64: ...estoring V VOL to P VOL To restore the V VOL to the P VOL 1 From the command prompt register the subsystem to which you want to restore the SnapShot pair then connect to the subsystem 2 Execute the aureplicationlocal command restore the pair First display the pair status and then restore the pair Refer to the following example aureplicationlocal unit subsystem name ss resync pvol 200 svol 1001 Are...

Page 65: ...fer to the following example The Snapshot pair is released aureplicationlocal unit subsystem name ss refer Pair name LUN Pair LUN Status Copy Type Group SS_LU0200_LU1001 200 1001 Split 100 SnapShot Ungrouped aureplicationlocal unit subsystem name ss restore pvol 200 svol 1001 Are you sure you want to restore pair y n n y The pair has been restored successfully aureplicationlocal unit subsystem nam...

Page 66: ...to the following example 2 Add the name to the group if necessary using command to change the pair information Refer to the following example 3 Create the next pair that belongs to the created group specifying the number of the created group with gno option SnapShot pairs that share the same P VOL must use same Data Pool 4 By repeating the step 3 the multiple pairs that belong to the same group ca...

Page 67: ... backup data aureplicationlocal unit UNITNAME ss resync pairname P_NAME gname G_NAME aureplicationmon unit UNITNAME evwait ss pairname P_NAME gname G_NAME st paired pvol REM Unmounting the P VOL pairdisplay x umount MAINDIR REM Splitting pair Determine the backup data aureplicationlocal unit UNITNAME ss split pairname P_NAME gname G_NAME aureplicationmon unit UNITNAME evwait ss pairname P_NAME gna...

Page 68: ...A 10 Operations Using CLI Hitachi Simple Modular Storage Copy on Write SnapShot User s Guide ...

Page 69: ...pShot Specifications B 1 Hitachi Simple Modular Storage Copy on Write SnapShot User s Guide SnapShot Specifications This appendix provides external specifications for SnapShot Snapshot General Specifications ...

Page 70: ... by a single V VOL Consistency Group CTG number Up to 256 consistency groups allowed per array Applies to SnapShot if used by itself or concurrently with ShadowImage For SMS100 up to 510 pairs can be assigned to a consistency group Data pools Maximum of 64 data pools controller data pool number is 0 to 63 Up to 64 volumes can be set for one data pool Up to 128 volumes per subsystem can be set for ...

Page 71: ... V VOL Only possible when P VOL and V VOL are in simplex status and not paired Swap V VOL for P VOL No Concurrent use with ShadowImage SnapShot and ShadowImage can be used at the same time on the same array However SnapShot volumes cannot be paired with ShadowImage volumes SnapShot use with expanded volumes Yes Concurrent use with LUN Manager Yes Concurrent use with Password Protection Yes Potenti...

Page 72: ...B 4 SnapShot Specifications Hitachi Simple Modular Storage Copy on Write SnapShot User s Guide ...

Page 73: ... B C D E F G H I J K L M N O P Q R S T U V W X Y Z Glossary This glossary provides definitions for replication terms as well as terms related to the technology that supports your Hitachi Simple Modular Storage 100 array Click the letter of the glossary section to display that page ...

Page 74: ...ks from the source volume to the target volume bps Bits per second the standard measure of data transmission speeds C cache A temporary high speed storage mechanism It is a reserved section of main memory or an independent high speed storage device Two types of caching are found in computers memory caching and disk caching Memory caches are built into the architecture of microprocessors and often ...

Page 75: ...torage systems Command devices are not used by ordinary applications Command devices can be shared between several hosts command line interface CLI A method of interacting with an operating system or software using a command line interpreter With Hitachi s Storage Navigator Modular Command Line Interface CLI is used to interact with and manage Hitachi storage and replication systems concurrency of...

Page 76: ...ous update cycle is available at all times on the remote storage system A consistent copy of S VOL data is internally pre determined during each update cycle and maintained in the remote data pool When remote takeover operations are performed this reliable copy is restored to the S VOL eliminating any data discrepancies Data consistency at the remote site enables quicker restart of operations upon...

Page 77: ... The data is updated from the differential data control status the pair volume is under the suspended status to the primary volume Differential Management Logical Unit DM LU The volumes used to manage differential data in a storage system In a TrueCopy Extended Distance system there may be up to two DM logical units configured per storage system For Copy on Write and ShadowImage the DM LU is an ex...

Page 78: ...ary volume to the secondary volume to make sure that both volumes are identical extent A contiguous area of storage in a computer file system that is reserved for writing or storing a file F failover The automatic substitution of a functionally equivalent system component for a failed one The term failover is most often applied to intelligent controllers connected to the same storage devices and h...

Page 79: ...pdate cycle Since only the differential data in the P VOL is transferred to the S VOL the size of data sent to S VOL is often the same as that of data written to the P VOL The amount of differential data that can be managed per write command is limited by the difference between the number of incoming host write operations inflow and outgoing data transfers outflow GUI Graphical user interface I I ...

Page 80: ...opposite of logical is physical which refers to the real organization of a system A logical description of a file is that it is a quantity of data collected together in one place The file appears this way to users Physically the elements of the file could live in segments across a disk logical unit See logical unit number logical unit number LUN An address for an individual disk drive and by exten...

Page 81: ...m where you mount your file systems or devices For a volume that is attached to an empty folder on an NTFS file system volume the empty folder is a mount point In some systems a mount point is simply a directory P pair Refers to two logical volumes that are associated with each other for data management purposes e g replication migration A pair is usually composed of a primary or source volume and...

Page 82: ...rom a primary site the application site onto the volumes of a secondary site the recovery site point in time logical copy A logical copy or snapshot of a volume at a point in time This enables a backup or mirroring application to run concurrently with the system pool volume Used to store backup versions of files archive copies of files and files migrated from other storage primary or local site Th...

Page 83: ...e maximum desired time period allowed to bring one or more applications and associated data back to a correct operational state It defines the time frame within which specific business operations or data must be restored to avoid any business disruption remote or target site Maintains mirrored data from the primary site remote path A route connecting identical ports on the local storage system and...

Page 84: ...ture secondary volume S VOL A replica of the primary volume P VOL at the time of a backup and is kept on a standby storage system Recurring differential data updates are performed to keep the data in the S VOL consistent with data in the P VOL SMPL Simplex snapshot A term used to denote a copy of the data and data file organization on a node in a disk file system A snapshot is a replica of the dat...

Page 85: ...in which a view of the primary volume P VOL is maintained as it existed at the time of the last snapshot The V VOL contains no data but is composed of pointers to data in the P VOL and the data pool The V VOL appears as a full volume copy to any secondary host volume A disk array object that most closely resembles a physical disk from the operating environment s viewpoint The basic unit of storage...

Page 86: ...s updated in the P VOL particularly when there are multiple write operations in one update cycle This feature is critical to maintain data consistency in the remote S VOL and is implemented by inserting sequence numbers in each update record Update records are then sorted in the cache within the remote system to assure write sequencing write workload The amount of data written to a volume over a s...

Page 87: ...editing 6 7 expanding 7 3 general 1 6 monitoring usage 7 3 requirements 2 9 sizing 2 5 specifications B 2 Threshold field 5 2 when data is deleted 6 5 deleting a pair 6 7 deleting a V VOL 6 7 designing the SnapShot system 2 1 Differential data deleted 6 5 Differential Management LUs description 1 6 disabling SnapShot 4 1 E editing data pool information 6 7 editing pair information 6 7 enabling Sna...

Page 88: ...1 5 enabling disabling 4 1 how it works 1 3 maintaining 7 2 overview 1 1 planning 2 1 restoring the P VOL operation 6 5 specifications B 1 snapshots how long to keep 2 3 how often to make 2 2 specifications B 2 splitting a pair 6 4 status definitions 7 2 Storage Navigator Modular 2 description 1 6 version 3 2 supported platforms 3 2 T tape backups 6 6 testing using the V VOL for 6 6 Threshold reac...

Page 89: ...1 Hitachi Simple Modular Storage Copy on Write SnapShot User s Guide ...

Page 90: ...95050 2627 U S A Phone 1 408 970 1000 www hds com info hds com Asia Pacific and Americas 750 Central Expressway Santa Clara California 95050 2627 U S A Phone 1 408 970 1000 info hds com Europe Headquarters Sefton Park Stoke Poges Buckinghamshire SL2 4HD United Kingdom Phone 44 0 1753 618000 info eu hds com ...

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