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

• It is not necessary to format a SVSP ThP virtual disk.
Why? All ThP pool reads to unwritten data will return “all zero” data.
• Restore only file backups, and never restore an image (sector based) backup into a ThP virtual
disk.
Why? Image backups are usually full virtual disk backups that do not differentiate between
data and free space (for example, a 10 GB virtual disk with 1 GB of actual data will have a
10 GB backup image, while a file backup will only be a 1 GB backup set). If an image backup
is restored on a ThP virtual disk, the full virtual disk space will be allocated in the ThP pool,
defeating the intent of ThP. On the contrary, a file backup restoration will only result in
restoring/allocating the space needed for the dataset from the ThP pool.
If a file backup of a ThP virtual disk takes too long (for example, when the ThP virtual disk contains
a large number of small files), there are two ways to mitigate this:
1. While using ThP virtual disks and creating files, create a fewer number of larger files whenever
possible. For example, while operating a database management system (DBMS) as in Oracle,
increase the size of the existing file by using a function for file extension—such as the auto
extended function of Oracle—instead of creating new files for table space extension of the
database.
2. Use a snapshot on the ThP virtual disk and then perform a tape backup from that snapshot.
NOTE: If users are not fully comfortable with using ThP for hosting their production data at first
release, it is recommended that the ThP virtual disk be mounted on the host as a single member
mirror set, to allow for future host-data migration. Many file systems (for example LVM and
OpenVMS Shadow) would allow the user to present a given virtual disk as a single member mirror
set. Here, a change of membership will be required when, for example, the user is to mirror the
ThP virtual disk to another ThP/traditional virtual disk. Then remove the original member after the
copy is fully accomplished. This will give the user a simple host-based method to migrate data off
the ThP virtual disk when needed, with the least application interruption.
Configuring ThP on SVSP—points to avoid
When configuring ThP on the SVSP, you should avoid:
• Mixing RAID levels in the ThP pool.
Why? This is to enable the most predictable and consistent ThP V-Vol performance.
• Mixing disk spindle speeds (example: 10K and 15K).
Why? This is to enable the most predictable and consistent ThP V-Vol performance.
• Mixing disk sizes (example: 36 GB, 72 GB, 146 GB, and so on)
Why? This is to enable the most predictable and consistent ThP V-Vol performance.
• Mixing disk types (different models).
Why? This is to enable the most predictable and consistent ThP V-Vol performance.
• Defragmenting a ThP virtual disk or using performance stress tools.
Why? This will result in undesirable storage pool space allocation (OS and tool dependent).
• Do not use init/erase from OpenVMS hosts (all versions) on ThP virtual disks.
Why? This will result in undesirable space allocation.
SVSP ThP thresholds and alarms
ThP virtual disk threshold
The virtual disk threshold is the percentage of the used or allocated capacity versus the total virtual
disk capacity. The threshold allows the user to define where they see the need for an alarm. You
72 Thin provisioning and operating system interaction