Categories: Offsite Vaulting, Alike DR, XenServer, Hyper-V, Alike v3, Alike v4
This article explains offsite maintenance operations in detail. Topics include understanding offsite state, resync and rebuild, purge, and reconcile.
Understanding Offsite State
The ODS data is housed in potentially millions of small files under the “blocks” subdirectory. Meta information about these blocks are stored in journals files that are creating during vaulting operations. As vaults complete, these journals are uploaded to the “journals” directory of your ODS.
When Alike needs to reconnect to its ODS, such as after a process restart, it will check these journals to see if its local installation is synced up with the offsite state. If you were in the process of vaulting when the services stopped, for example, Alike will need to reverse this vaulting operation before new operations can take place. This process is called resyncing. If there is considerable discrepancy, Alike will require that the local state is rebuilt.
Resync and Rebuild
Both resync and rebuild will “roll out” failed or cancelled vault jobs by deleting blocks that were uploaded but not committed. If Alike was in the process of deleting a vault, either due to user instruction or during a scheduled offsite maintenance job, this delete operation will also be finished during resync or rebuild.
Both resync and rebuild operations will work faster if reconcile is run frequently. This is because reconcile consolidates and reduces the number of journal files offsite. Rebuild in particular will benefit from regular reconciliation.*
Unlike local backups, Alike will not automatically purge older offsite versions that are beyond your retention settings. For example, if you retain 5 versions of your VM onsite and 5 versions offsite, Alike will automatically delete the oldest 6th version onsite after five backups are made, and perform this work in the background when jobs are not running.
However, Alike WILL NOT delete your 6th vault in the background. Instead, to give you control of your bandwidth usage, this process is run explicitly during a weekly maintenance operation. You can configure this maintenance operation under Settings > Offsite. By default, purge and reconcile are run together every Sunday at midnight.
You can also select an offsite version under Windows Explorer and purge it manually by right-clicking on it and selecting “Purge this Version from Remote Storage.” If you do this, the purge will be run immediately in a new job.
Reconcile is a process that applies outstanding journals on the remote ODS. Once reconcile is completed, there will be fewer journals offsite, and sync operations will be accelerated. Reconcile must download a large amount of offsite meta information, and for this reason, can take a long time over slower connections. Reconcile can run while other vault operations are performed, but it must be run weekly in order to maintain the health and performance of your ODS.
By default, Alike schedules a reconcile to run every Sunday immediately after offsite purge at midnight. You can change this schedule under Settings > Offsite. If you disable offsite reconciliation, Alike vault jobs will warn you after a week has passed without reconciliation. If enough time passes without reconcile, your vault jobs will fail.
*Please Note: It is not necessary to run resync or rebuild in order to restore data from offsite. Restores can be conducted IMMEDIATELY, skipping this process entirely.