Storix Software SBAdmin User Guide - Manual (Page 87)

If using Workstation Edition, the Client entry box at the top does not appear. If using Network Edition, you must
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 or ZFS datasets on that system will be displayed in the second listbox.
You must either select the individual logical volumes or ZFS datasets for which snapshots may be created, or
select “all”. If “all” is selected, snapshots will be permitted for all supported snapshot 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, and then referred to in place 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
Storix System Backup Administrator 87 Version 8.2 User Guide