HP StoreOnce Backup System Concepts and Configuration Guidelines (BB877-90913, November 2013)

14 Housekeeping
Housekeeping is the process whereby space is reclaimed and is best scheduled to occur in quiet
periods when no backup or replication is taking place. If insufficient time is allocated to
housekeeping, there is a risk that housekeeping jobs will stack up – effectively “hogging” capacity
So, there are two factors to consider:
• Is housekeeping interfering with performance, in which case you may wish to set blackout
windows, when housekeeping will not occur, see below.
Housekeeping blackout windows are configurable (up to two periods in any 24 hours) so,
even if the “clean up” scripts run in the backup software, the housekeeping will not trigger
until the blackout window is closed.
• Are backup and replication jobs scheduled to allow housekeeping time to complete?
Running backup, restore, tape offload and replication operations with no break (i.e. 24 hours
a day) will result in housekeeping never being able to complete. Configuring backup rotation
schemes correctly is very important to ensure the maximum efficiency of the product; correct
configuration of backup rotation schemes reduces the amount of housekeeping that is required
and creates a predictable load. For example, large housekeeping loads are created if large
numbers of cartridges are manually erased or re-formatted. In general all media overwrites
should be controlled by the backup rotation scheme so that they are predictable.
Housekeeping also applies when data is replicated from a source StoreOnce appliance to a
target StoreOnce appliance – the replicated data on the target StoreOnce appliance triggers
housekeeping on the target StoreOnce appliance to take place. Blackout windows are also
configurable on the target devices.
Housekeeping Blackout window
This is a period of time (up to 2 separate periods in any 24 hours) that can be configured in the
StoreOnce appliance during which the I/O intensive process of Housekeeping WILL NOT run. The
main use of a blackout window is to ensure that other activities such as backup and replication
can run uninterrupted and therefore give more predictable performance. Blackout windows must
be set on BOTH the source StoreOnce appliance and Target StoreOnce appliance. See HP
StoreOnce Backup system Best Practices with Sizing Tool and StoreOnce Catalyst worked examples
for a fully worked example of configuring a complex StoreOnce environment including setting
housekeeping windows.
NOTE: With the HP B6200 Backup system, housekeeping blackout windows are configured per
service set.
Without a housekeeping blackout window set, the housekeeping can interfere with the backup
jobs because both are competing for disk I/O.
By setting a housekeeping blackout window appropriately from 12:00 to 00:00 we can ensure
the backups and replication run at maximum speed because the housekeeping is scheduled to run
when the device is idle.
There is a worked example in HP StoreOnce Backup system Summary of Best Practices with Sizing
Tool and StoreOnce Catalyst worked examples.
Tuning housekeeping using the StoreOnce GUI
Some tuning is required to determine how long to set the housekeeping windows; this is achieved
using the StoreOnce Management Interface and the reporting capabilities which we will now
explain.
106 Housekeeping