Migrating Virtual Disks; Virtual Disk Cache Policies; Virtual Disk Write Cache Policies - Dell PowerEdge VRTX User Manual

Migrating Virtual Disks

You can migrate virtual disks from another system's Shared PERC 8 controller when the target system is either turned on
or off.
Migrating Virtual Disks If The Target System Is Turned Off
1. Turn off the source system.
2. Move the appropriate physical disks from the source system to the target system with a similar Shared PERC 8
controller.
3. Turn on the target system.
The system discovers and automatically imports the detected foreign configuration.
Migrating Virtual Disks If The Target System Is Turned On
1. Turn off the source system.
2. Move the appropriate physical disks from the source system to the target system with a similar Shared PERC 8
controller.
3. Access the Dell Chassis Management Controller (CMC) to import and clear the foreign configuration.
NOTE: For more information on the CMC for Shared PERC 8, see the
Dell PowerEdge VRTX User's Guide at dell.com/esmmanuals.

Virtual Disk Cache Policies

The following Virtual Disk Cache policies are supported on Shared PERC 8:
•

Virtual disk write cache policies

• Virtual disk read cache policies
Virtual Disk Write Cache Policies
The write-cache policy of a virtual disk determines how the controller handles writes to the virtual disk. Write-Back and
Write-Through are the two write cache policies that can be set on virtual disks individually.
All RAID volumes are presented as Write-Through to the operating system independent of the actual write cache policy
of the virtual disk. The Shared PERC 8 cards manage data in the cache independently of the operating system or any
applications.
NOTE: Use the Dell Chassis Management Controller (CMC) to view and manage virtual disk cache settings.
Write-Back
In Write-Back caching, the controller sends a data transfer completion signal to the host when the controller cache has
received all the data in a transaction. The controller then writes the cached data to the storage device in the
background.
The risk of using Write-Back cache is that the cached data can be lost if there is a power failure during or when the data
is written to the storage device. This risk is mitigated by using a Non-Volatile Cache on the Shared PERC 8 card.
NOTE: The default cache setting for virtual disks is Write-Back caching.
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