Planning capacity

Aspects of capacity planning

The following are aspects of capacity planning:

SnapVault secondary storage system volume size
LockVault log volume size
Number of qtrees backed up to each volume
SnapVault schedule

Guidelines for the secondary storage system volume size

The following are conservative guidelines you can use to estimate the size of SnapVault secondary storage system volumes for growth over one year, depending on how often you back up data.

Three percent (3%) growth every day
Five percent (5%) growth every week
Ten percent (10%) growth every month
Seven percent (7%) monthly growth rate, compounded to 100 percent growth every year

Daily backup example

Assuming a starting baseline transfer of 1 GB and 100 percent growth of new data for the year (1 GB). The changed size due to daily growth if changes are made every weeknight is as follows:

Size due to daily growth = (number of days x .03) - (new data)

= (250 x .03) - 1 GB = 7.5 GB - 1 GB = 6.5 GB of change

Therefore, for 1 GB of source data, you need 1 GB baseline + 1 GB new data + 6.5 GB of changed data = 8.5 GB secondary system volume. In other words, you must be able to scale the secondary system volume to about 8 times the current data set size within one year.

Weekly backup example

Using the same assumptions as the daily backup example, the changed size due to weekly growth if changes are made every week is as follows:

Size due to weekly growth = (number of weeks x .05) - (new data)

= (52 x .05) - 1 GB = 2.6 GB - 1 GB = 1.6 GB of change

Using weekly backups, for 1 GB of source data, you need 1 GB baseline + 1 GB new data + 1.6 GB of changed data = 3.6 GB, or a scaling factor of a little over 3.5 times the current data set size with one year.

Guidelines for LockVault log volume size

Consider the following guidelines to estimate the log volume size:

Baseline transfer = number of inodes per volume x 256 bytes
where 256 bytes is an estimated size of the log entry.
Incremental transfers = number of inodes x .03 x 250 Snapshot copies x 256 bytes, where .03 represents the rate of change.

Use these guidelines to estimate the size of the log data associated with each SnapLock volume and create a log volume equal to the total of the combined estimated sizes.

Note
If the estimate is too low, you can add disks to the volume; alternatively, you can allocate a second log volume if the first becomes full and configure the system to use the new log volume.

Guidelines for number of qtrees backed up to a volume

Use the following guidelines when backing up qtrees to a volume using SnapVault:

Because of performance constraints, a maximum of 16 primary qtrees should be backed up to a single secondary volume.
To gain optimum performance, the number of qtrees backed up to a volume should be approximately six.
If you are backing up volumes to qtrees using SnapVault, a maximum of 16 volumes should be backed up to a volume.
Note
You can mix backed up volumes and qtrees on the same secondary volume, if desired.

Guidelines for scheduling SnapVault transfers

The only guideline for scheduling SnapVault transfers is to not overload the primary storage system or the network. You must consider the overall load and time to complete all transfers.