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Overlapping backups to minimize housekeeping interference
Source 1 – Bad scheduling
Source 2 – Good scheduling
As backup DIR 1 finishes it triggers
Housekeeping, which then impactsthe
performance of the backup on DIR 2
If backup jobs can be scheduled to cpmplete at
the same time, the impact of Housekeepong on
backup performance will be geatly reduced
The HP D2D Backup Systems have the ability to set blackout windows for replication, when no replication will
take place – this is deliberate in order to ensure replication is configured to run ideally when no backups or
housekeeping are running.
In the worked example let us assume the following time zones
Sites A and D = GMT + 6 (based in APJ)
Sites B and C = GMT - 6 (CST in US)
Site E = GMT (based in UK)
All time references below are standardized on GMT time. Replication blackout windows are set to ensure
replication only happens within prescribed hours. In our example we input the replication window as 12 hours,
but we would have to edit this to 8 hours to conform to the plan below.
Site
Backup
Replication
Housekeeping
A
12:00 – 20.00
20:00 – 04:00
04:00 - 12:00
B
24:00- 08:00
08:00-16:00
16:00-24:00
C
24:00- 08:00
08:00-16:00
16:00-24:00
D
12:00 – 20.00
20:00 – 04:00
04:00-12:00
E
18:00 – 02:00
08:00 – 04:00
02:00 – 10:00
As you can see from the above worst case example, with such a worldwide coverage, the target device E
cannot easily separate out its local backup (18:00 – 02:00) so that it does not happen at the same time as the
replication jobs from sites A, B, C, D and the housekeeping required on device E.
What this means is that the replication window on the target device must be open almost 24 hours a day or at
least 08:00 to 04:00. The target device essentially has a replication blackout window set only between the hours
of 04:00 and 08:00 GMT.
In this situation the user has little alternative but to OVERSIZE the target device E to the next model up with higher
I/O and throughput capabilities in order to handle this unavoidable overlap of local backup, replication from
geographically diverse regions and local housekeeping time. There are two ways of ensuring enough I/O
capability on the target. Upsize again to a two-shelf D2D4106. Or configure two housekeeping windows in the
24-hour period to alleviate congestion at the target site.