VERITAS Storage Foundation 4.1 for Oracle RAC HP Serviceguard Storage Management Suite Extracts, December 2005

Performance of Storage Checkpoints
If you are restoring some of the files in the file system, you should first remove the
data-full Storage Checkpoints that are no longer needed. If you have very limited free
space on the file system, you may have to remove all data-full Storage Checkpoints in
order for the restore to succeed.
Always reserve free disk space for growing volumes and file systems. You can also
preallocate sufficient space for each file system when the file system is first created or
manually grow the file system and logical volume where the file system resides. See the
vxassist(1) and fsadm_vxfs(1) manual pages for more information.
Performance of Storage Checkpoints
VxFS attempts to optimize the read and write access performance on both the Storage
Checkpoint and the primary file system. Reads from a Storage Checkpoint typically
perform at nearly the throughput of reads from a normal VxFS file system, allowing
backups to proceed at the full speed of the VxFS file system.
Writes to the primary file system are typically affected by the Storage Checkpoints
because the initial write to a data block requires a read of the old data, a write of the data
to the Storage Checkpoint, and finally, the write of the new data to the primary file
system. Having multiple Storage Checkpoints on the same file system, however, will not
make writes slower. Only the initial write to a block suffers this penalty, allowing
operations like writes to the intent log or inode updates to proceed at normal speed after
the initial write.
Reads from the Storage Checkpoint are impacted if the primary file system is busy,
because the reads on the Storage Checkpoint are slowed by all of the disk I/O associated
with the primary file system. Therefore, performing database backup when the database
is less active is recommended.
For more information on Storage Checkpoints and Storage Rollback, see the VERITAS File
System Administrator’s Guide.
132 VERITAS Storage Foundation for Oracle RAC Installation and Configuration Guide