Data retention question...

Last post 05-27-2011, 1:57 PM by Jeff D. 6 replies.
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  • Data retention question...
    Posted: 05-15-2011, 9:26 PM

    Ok, so the way I have my policy planned there's a month's worth of data being kept deduplicated on disc through retention.  All jobs are being aux copied to tape but those tapes are being cycled and thus constantly overwritten.  I also have the deduped data being SILO'd and those tapes are not being overwritten.  Will the data on those SILO tapes be retrievable after the retention on the data stored on the maglib has expired and it's pruned?

    And I guess I should say easily retrievable, because if I have to pull the chunks in via media explorer and whatnot then I would consider the answer no, heh.  My hope is to keep data SILO'd and archived so I can have point-in-time recovery for as far back as I want go.  I understand this goes down the drain once I have to seal the store for any reason and as such I will also selectively aux copy fulls from time to time and archive, but being able to recover from any day would be great instead of just the moments I've selectively aux copied.

    Just my 1.4 cents (after taxes)
  • Re: Data retention question...
    Posted: 05-17-2011, 1:12 PM

    Anyone?  I guess the simpler question would be is job history kept after the data retention date and can SILO'd data beyond that time be used to perform recoveries?

    Just my 1.4 cents (after taxes)
  • Re: Data retention question...
    Posted: 05-17-2011, 3:04 PM

    data being silo'ed should be retrievable and the silo restoration should occur automatically, when the request data is required.  Remember that even if you need a single file from an old backup, the entire job and data associated with the silo is required to get the data back.  In theory a single file restore could rehydrate gigs worth of data, so ensure you maglib has the free space.

  • Re: Data retention question...
    Posted: 05-17-2011, 3:11 PM

    Yea, space is no problem, I was just worried that when the data was pruned off the maglib that it also pruned the job/file history as well, making retrieval difficult.  But as long as the jobs are still visible and it will pull the necessary SILO data for the recovery I'm happy.

    Just my 1.4 cents (after taxes)
  • Re: Data retention question...
    Posted: 05-26-2011, 2:50 PM

    My Commvault rep told me opposite, so now I'm confused.  He said that SILO data would be unavailable after the retention time since SILO is only intended to be used as a temporary way to offload data from speedy/expensive storage to slower/cheaper storage until the retention time is met.

    So I guess the question is, if I have a retention of 30 days set on my storage policy and all the data is being SILO'd, after 30 days when that data is aged off the maglib, will I still be able to pull it from the SILO?  Will the jobs representing that data still be indexed?

    Just my 1.4 cents (after taxes)
  • Re: Data retention question...
    Posted: 05-27-2011, 1:50 PM

    Silo is defined as:

    Silo Storage enables you to store deduplicated backups on secondary storage devices. The ability to store deduplicated data on secondary storage reduces the storage requirements and facilitates longer retention periods. The efficient use of storage space enables storing large volumes of backup data, which reduces the cost of backup storage and long term data retention.

    Silo Storage also enables effective use of the primary disk storage by managing the disk space and periodically moving the data to the Silo Storage. This efficient disk management reduces the cost of storage.

    Silo Storage provides the ability to store deduplicated data in tapes. This is performed as follows:

    • Backup data from clients is first deduplicated in a primary disk.
    • The deduplicated data, which includes the deduplication store and the data (called as Silos), are then copied to tape by running a Silo backup job.
    • During a restore operation, if the data is available in disk it is restored from the disk. If the data is not available, then the necessary tapes are accessed to bring back the data to the disk, and then restored to the client.

    To directly answer your question; If the primary is siloed it will only be on tape for the extent of the retention.  Now if you Silo'ed your dash copy that can be your extended rentention silo copy. 

    In a tier scenario, this makes sense as your Fast primary disk is DASH'ed to slower secondary disk then silo'ed to tape.


  • Re: Data retention question...
    Posted: 05-27-2011, 1:57 PM


    Ah, I was afraid of that.  Unfortunately in our environment I don't have the luxury of another tier of maglib storage to achieve this.  I do however have plenty of space on my primary maglib for the forseeable future, so this essentially comletely invalidates the SILO functionality for us unless I up the retention period on data, but since it's deduped I run the risk of introducing performance issues if I push it's retention too far.  Heh, sounds like a lose-lose for me.  Thanks for the info though.  That certainly clearly answers my question.

    Just my 1.4 cents (after taxes)
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