Adaptec 5325301656 Administration Guide - Page 111

Estimating Snapshot Pool Requirements Snapshots and iSCSI Disks Running a snapshot on a volume containing an iSCSI Disk will abruptly disconnect any clients attempting to write to the iSCSI Disk and the resulting snapshot may contain inconsistent data. Do not use snapshots on a volume containing an iSCSI Disk. Estimating Snapshot Pool Requirements Snapshot data grow dynamically for as long as a snapshot is active and as long as there is enough space available in the snapshot pool to store them. When the snapshot pool approaches its capacity (at about 95 percent), the Snap Server deletes the oldest snapshot's data to create space for more recent snapshot data. The default configuration allocates 80 percent of RAID capacity to the volume and 20 percent to the snapshot pool. You can adjust the size of the pool up (assuming unallocated space exists) or down according to your needs. If you find that your snapshot strategy does not require all of the space allocated to the snapshot pool by default, consider decreasing snapshot pool capacity and reallocating the capacity to the file system. To adjust the size of the snapshot pool, navigate to the Storage > Snapshots screen, and click the Adjust Snapshot Space link in the introductory text. The number of snapshots that a RAID can support is a function of these factors: • The space reserved for the snapshot data • The duration of the snapshots you create • The amount and type of write activity to the volume(s) since the snapshot was created The following table describes minimum and maximum allocation cases. Allocate about 10% of RAID if Allocate about 25% of RAID if • Activity is write-light • Activity is write-heavy • Write access patterns are concentrated in • Write access patterns are randomized a few places across the volume • A small number of Snapshots must be available at any point in time • A large number of Snapshots must be available at any point in time Chapter 7 Snapshots 97