HP D2D D2D Best Practices for VTL, NAS and Replication implementations (EH985- - Page 101
Source 1, Bad scheduling, Source 2, Good scheduling
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Overlapping backups to minimize housekeeping interference Source 1 - Bad scheduling As backup DIR 1 finishes it triggers Housekeeping, which then impactsthe performance of the backup on DIR 2 Source 2 - Good scheduling 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. 101