Adaptec 5325301638 - Snap Server 4500 NAS, Administrator'S Manual

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iSCSI Disk Management and Usage
Chapter 5 iSCSI Disks 43
without some risk. If the Snap Server were to suddenly lose power, for example,
data still in cache would be lost.
This risk can be minimized by following industry-standard security precautions
such as keeping servers in a secured location and connecting power supplies to the
mains using a network-based UPS. In most environments, taking these simple
precautions virtually eliminates the risk of serious data loss from sudden and
unexpected power outages.
Of course, the physical conditions and company policies that guide IT decisions
vary widely. Power outages are a common occurrence in some areas, and data
protection procedures vary from company to company. Administrators who
determine that the risk of data loss, even with security cautions in place, outweighs
the significant increase in write performance that write-cache provides, can disable
this feature for individual iSCSI Disks.
Tips
(1) Write-cache can be disabled on an iSCSI Disk-by-iSCSI Disk basis.
Disabling write-cache for an iSCSI Disk does not disable write-cache for any other
iSCSI Disk or any other resources on the Snap Server; (2) The opportunity to
enable/disable write-cache for an iSCSI Disk occurs only when the disk is created; it
cannot be toggled at a later date; (3) Disabling write-cache for an iSCSI Disk does
not eliminate
all potential risk of data loss due to an unexpected loss of power as
each disk drive contains its own internal cache of 8MB or more.
Disconnect iSCSI Disk Initiators before Shutting Down the Server
Shutting down the server while a client initiator is connected to an iSCSI Disk
appears to the client initiator software as a disk failure and may result in data loss
or corruption. Make sure any initiators connected to iSCSI Disks are disconnected
before shutting down the server.
Ignore the Volume is Full Message
When an iSCSI Disk is created, the volume allocates the specified capacity to the
disk. If all volume capacity is allocated to the iSCSI Disk and e-mail notification is
enabled, the Snap Server may generate a
Volume is Full message. This message
indicates only that the volume capacity is fully allocated to the iSCSI Disk and is not
available to other resources. To determine the status of iSCSI Disk storage
utilization, use the tools provided on the client machine.