Storix Software SBAdmin TSM Edition Users Guide - Manual (Page 51)

First, select the client for which to configure snapshots by pressing the arrow next to the Client name field.
After doing so, a list of logical volumes/ZFS datasets on that system will be displayed in the second listbox.
You must either select the individual device for which snapshots may be created, or select “all”. If “all” is
selected, snapshots will be permitted for all applicable devices.
Again, you must also select to Perform Snapshot Backup? from the job configuration
screen before a snapshot of a logical volume or filesystem will be created.
The options which follow indicate the action the backup process should take when performing snapshot
backups:
1. Size (%):
For each logical volume (or for “all” if selected), indicate the size of the snapshot as a percentage of the
original LV. The size needed will depend on the amount of data that is changed within the original LV while
the backup is in progress. It is very important to create the snapshot large enough that it does not run out of
space.
2. Chunk size (Kbytes):
Use the arrow to the right of the entry field to list and select from a valid chunk size. Valid sizes are from 4
Kbytes to 1024 Kbytes (1 megabyte).
A “chunk” is the unit in which the original logical volume will be divided when tracking changes to the LV
when a snapshot is used. Each time a chunk is changed for the first time, the original chunk is copied to the
snapshot LV in its entirety, then referred to instead of the original by the backup process.
When determining the best chunk size to use, there is a trade-off: The larger the chunk, the fewer writes to
the original LV it will take to fill up the snapshot LV (since larger chunks of data must be copied, even when
only a small piece of data is changed). The smaller the chunk, the more individual copies must occur as the
original data is changed, which may have a greater impact on system performance during the backup. The
default of 64 Kbytes is sufficient for most purposes.
3. When backing up this client, create snapshots of filesystems:
Storix System Backup Administrator 51 Version 8.2 TSM Edition User Guide