Storage Management Overview
51
NAS 2000s Administration Guide
Advantages
Distributed data guarding offers:
■
High read and write performance
■
Protection against data loss if one drive fails
■
Increased usable storage capacity, since capacity equal to only one physical drive is used
to store parity information
Disadvantages
Some disadvantages of distributed data guarding are:
■
Lower write performance than RAID 0 or RAID 1+0
■
Possibility of data loss if a second drive fails before data from the first failed drive has
been rebuilt
RAID ADG—Advanced Data Guarding
RAID ADG is similar to RAID 5 in that parity information is generated (and stored) to protect
against data loss caused by drive failure. With RAID ADG, however, two different sets of
parity data are used. This allows data to still be preserved if two drives fail. As can be seen
from
, each set of parity data uses up a capacity equivalent to that of one of the
constituent drives, for a total parity usage of two drives of space.
This method is most useful when data loss is unacceptable, but cost must also be minimized.
The probability that data loss will occur when configured with RAID ADG is less than when
configured with RAID 5.
Note:
The ADG feature is available only with the optional Smart Array 5304/6404 Controller
installed.
Figure 26: RAID ADG (advanced data guarding) with two sets of parity data
Advanced Data Guarding technology offers the best combination of fault tolerance and usable
disk space among RAID levels.
B1
B3
P5,6
Q7,8
B2
B7
P3,4
Q5,6
B5
B8
P1,2
Q3,4
B4
B6
P7,8
Q1,2
Содержание 345646-001 - StorageWorks NAS 2000s External Storage Server
Страница 16: ...About this Guide 16 NAS 2000s Administration Guide ...
Страница 56: ...Storage Management Overview 56 NAS 2000s Administration Guide ...
Страница 80: ...Disk Management 80 NAS 2000s Administration Guide ...
Страница 93: ...Shadow Copies 93 NAS 2000s Administration Guide Figure 46 Accessing shadow copies from My Computer ...
Страница 110: ...User and Group Management 110 NAS 2000s Administration Guide ...
Страница 146: ...Folder Printer and Share Management 146 NAS 2000s Administration Guide ...
Страница 151: ...Microsoft Services for NFS 151 NAS 2000s Administration Guide Figure 83 Server for NFS screen Server Settings tab ...
Страница 186: ...NetWare File System Management 186 NAS 2000s Administration Guide ...
Страница 200: ...Index 200 NAS 2000s Administration Guide ...