BLOB files on the external file store may become orphaned in a number of ways including being purged from the SharePoint Recycle Bin. SharePoint also generates a substantial number of orphaned BLOBs in the course of its normal operations. For example, when a document is checked out, modified and checked back in, SharePoint may write out an entirely new copy of the BLOB file and abandon the old one.
The Unused BLOB Cleanup Job removes these orphaned BLOBs from the external file store. It is important to schedule and run this job on a regular basis to reclaim space on the external file store and stop the file store from growing too large with unused BLOB files. However, there are several considerations to take into account when scheduling this job.
The Unused BLOB Retention is a setting on each profile that specifies how many days after being orphaned that a BLOB file should be retained. So instead of deleting the BLOB immediately after being orphaned, the Unused BLOB Cleanup Job will retain the BLOB for a specified number of days.
This setting is important for synchronizing the BLOB store around the backup/restore cycle. The Unused BLOB setting allows for restoring older backups of the content database without restoring backups of the file store. Backups of the content database as old as the retention setting can be safely restored without also restoring the file store. This setting is particularly important if the backup cycles of the content database and file store are not synchronized.
The Unused BLOB retention setting also allows for item level restore using other Metalogix products. In this case, the BLOB retention must be set to the maximum number of days in the past that deleted items can be restored. So, for example, if the retention is set to 180 days, then any SharePoint documents or list items deleted in the last 180 days could be safely restored.
In certain situations, sites may be deleted, but kept in an indefinite hold in a secondary recycle bin. SharePoint still marks this site as deleted, and therefore, the Unused BLOB Cleanup job may mark the BLOBs of that site for deletion, if the profile retention policy has been met. So even though the site is still within the restore window for the recycle bin, the BLOBs may not be. It is important to correlate these timeframes when configuring profiles and recycle bin retention policies. For more information, please contact Quest Support.
The Unused BLOB Cleanup Job should be run on a regular basis to keep the file store from becoming cluttered with orphaned BLOB files. When creating a new profile, it will default to weekly. However, how frequently it should run depends on several factors:
·How active is the SharePoint site? If the site has users performing lots of check-in/checkout activity or deletion of files, then the file store could see large numbers of orphaned BLOB files start to accumulate.
·How large are typical files in use on the site? If very large files are being manipulated or uploaded to the site, then the BLOB store could see a sizeable amount of space devoted to orphans. However, if the files are small, then this may not be a major concern.
·How big is the content database? If the content database has large numbers of documents, then the Unused BLOB Cleanup job make take several hours to run. This means that the job must be carefully scheduled around backup/restore and other maintenance windows.
·How many content databases are there in the farm? If there are a large number of content databases in the farm, then each will need its own Unused BLOB Cleanup Job scheduled. These need to be carefully scheduled to avoid overloading the WFE servers or database servers.
·How much slack space does the BLOB store have? If the BLOB store has plenty of room to expand (and then shrink once the cleanup job runs), then running the Unused BLOB Cleanup Job less frequently may be viable option. However, if space is tight, then the job may need to be scheduled to run more often.
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