HP StorageWorks SAN Virtualization Services Platform Best Practices Guide (5697-0935, May 2011)

SVSP supports two types of PiTs:
• Crash consistent—Occurs if I/O continues to the virtual disk during PiT creation.
• Transaction consistent—Occurs when the application has been stopped and the cache has
been flushed to the device (can be accomplished by unmounting the device from the host).
Additional information about PiTs:
• PiTs start at 0.5 GB, and grow by the smaller of current temporary virtual disk size, or 5% of
the original virtual disk size.
• The minimum time between successive PiTs for SVSP v3 is 10 minutes.
• Create a virtual disk group for all virtual disks that need to be synchronized for PiT creation.
The following tools are available for PiTs:
• VShadow—Works with Windows 2008 and the VSS HW Provider. The VSS HW Provider
does not support synchronous mirrored objects or virtual machines. See the HP StorageWorks
SAN Virtualization Services Platform Administrator Guide for information about installing and
using VSS.
• Exchange CCR—Use for Microsoft Exchange 2007.
• SQL2008—Use the Database Mirroring feature.
• Microsoft Office Sharepoint Server (MOSS) 2007—Create EVA snapshots using Microsoft
Data Protection Manager and integrate with MOSS 2007.
NOTE: HP does not recommend that you completely eliminate or replace your backup
infrastructure with PiTs and snapshots. A multi-leveled disaster recovery replication scheme is
generally recommended to protect against differing forms of disaster—physical, human, and IT.
Your HP storage specialist can give advice for your specific needs.
The benefits of snapshots are:
• Zero impact backups—You can perform virtual disk backups by regularly creating a PiT of
the virtual disk. Create a snapshot on the PiT and mount it on a backup server. Run your
backup application on the mounted snapshot. When the backup is complete, you can unmount
and delete the snapshot, and then delete the PiT. Backups can occur at any time of the day
while the production systems remain online and fully available during backup. The solution
uses zero CPU cycles on production servers and zero LAN resources. Data can be restored
from PiTs within minutes using the PiT rollback feature. However, the rollback PiT operations
is always done offline, that is, host presentations need to be removed. Once the rollback
operation is complete, the unit should then be re-presented. Unmounting causes the host to
flush to disk, which needs to happen before the rollback.
• Accelerated application testing—A snapshot enables you to radically reduce the time needed
to prepare data for test runs. Copying and staging data is reduced to minutes for each test
run. Instead of copying data for each test run, you create a PiT of the development virtual
disk. This enables you to create as many snapshots of the PiT as you want, and test
modifications in parallel on the snapshots. If modifications introduce problems, you can simply
delete the affected snapshots, without losing your original data. If you want to keep
modifications that you performed on one of the snapshots, you can use the Restore feature to
replace the original virtual disk with the snapshot. PiT creation, snapshot creation, and restore
are all fast operations that complete in minutes.
38 Data migration