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

1 At FS creation time, the capacity of the storage pool is consumed up to 100% of the ThP virtual disk capacity.
2 At FS creation time, the capacity of the storage pool is consumed up to 30% of the ThP virtual disk capacity.
3 VMware eagerzeroedthick formatting is not recommended because it will force the virtual disk to fully allocate space
in the storage pool.
4 ZFS "zpool scrub" is not recommended to use because it will force the virtual disk to fully allocate.
5 Oracle is known to write (zeros) to unused blocks.
Oracle 11g and ThP
HP strongly recommends using “Auto Extend” while using Oracle with ThP (to take advantage of
ThP). While using the Oracle “Auto Extend”, it was observed that Oracle extends the partition
before it fully uses the granted space (ThP/non ThP virtual disks—critical threshold).
Do not put swap space and redo-log space in ThP V-vol; use normal virtual disks due to excessive
write I/O.
Auto-extend
The Auto-Extend feature of the Oracle database allows tablespaces to extend their size on an as
needed basis, which integrates well with ThP by pre-allocating ThP pages to improve performance.
Initially, Auto-Extend consumes a very small amount of capacity to prevent excessive ThP page
allocation at tablespace creation. Plus, ASM working with ThP can help reduce the complexity of
handling virtual disks as they fill up over time.
VMware support using SVSP ThP
The investigations were done to examine the impact of VMware on ThP pool space allocation.
• VMware can use the storage device as VMFS, Raw, or RDM (raw device mapped).
• VMFS is the common and preferred file system, however, using the ThP as thin device is the
ideal way if compared to thick device.
• VMware eagerzeroedthick formatting is not recommended (results full allocation).
ResultsRange of accessItem
GoodTop only (500 MB)Make VMFS
GoodTop, middle, and end (3 GB)Make FS in Guest OS (Windows
2003)
Good (the same as when there is no
VMware)
32 GB (total)Make FS in Guest OS (Linux EXT3)
Migrating data from a ThP V-VOL to another ThP V-VOL will only write allocated pages from one
storage pool to the other. First data is exchanged between the pools. After the pool information is
exchanged, the host presented V-VOL is swapped with the Auto-LUN V-VOL by simply pointing the
original V-VOL to the address in the new pool’s VFS/DMT.
76 Thin provisioning and operating system interaction