SILO Questions

Last post 07-15-2013, 1:08 PM by Ali. 3 replies.
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  • SILO Questions
    Posted: 07-05-2013, 6:31 PM

    Trying to understand the nuances of SILO storage policies.  So far, as I understand it, once a SILO job is run all data in the dedupe store is copied to tape, it is then be purged from the maglib storage assuming cached copies isn't enabled.

    Once the data is purged from the maglib, when additional backups are written to the storage policy, that would normally contain significant duplicate data already in the SILO, will it write only the unique blocks to the maglib or does it write the entire dataset again, deduping only against what isn't SILOed? 

    I would hope it would only write the unique blocks, which will then get SILOed when the job runs again.  Can anyone clarify this?

    I intend to use a SILO in order to extend the storage available for us for on-site extended retention copies.  The next question would be, when retention is met and unique blocks are purged through data aging, does that space then become available on the tapes in order to write additional data to or will it wait till all data is purged?

  • Re: SILO Questions
    Posted: 07-06-2013, 11:46 PM
    • Ali is not online. Last active: 07-03-2019, 12:32 PM Ali
    • Top 10 Contributor
    • Joined on 08-05-2010

    Hi jake, you're pretty much on the mark, just a few clarifications.

    1.  Yes, only unique blocks will be written, same princle for dedupe applies to SILO or non-SILO no differnce there, so in other words wether or not the data is written to SILO Tape or not, only unique blocks are written to disk, of course if you seal the Store, now you're going to lay down a new footprint.

    2.  Data Aging will not do the 'purging' it will be Managed Disk Space thresholds set at the Library level which will control (primarily) when the purging can occur.  This way regardless of retention (since you're going to have long term) you don't have to worry about how 'long' you'll keep the data on disk, its 'when' the library fills up, the system will self-manage that.

    3.  Check out this BOL section, explains a lot about the overall process:

    http://documentation.commvault.com/commvault/release_9_0_0/books_online_1/english_us/prod_info/dedup_tape.htm?var1=http://documentation.commvault.com/commvault/release_9_0_0/books_online_1/english_us/features/dedup_tape/advanced.htm

  • Re: SILO Questions
    Posted: 07-15-2013, 12:54 AM
    Regarding the last question, tapes are sequential media and whether it is SILO or conventional backups to tape, it will still need all data on the particular tape itself to have met retention and aged off before you can reuse the tape.
  • Re: SILO Questions
    Posted: 07-15-2013, 1:08 PM
    • Ali is not online. Last active: 07-03-2019, 12:32 PM Ali
    • Top 10 Contributor
    • Joined on 08-05-2010

    True what jordanxu said, just a key point to note, for SILO its not job based "Tape" aging, its "Store Based" once that Store ages, all the media comes back, and for SILO tapes, you won't have 'backup jobs' on those tapes, only SILO Archive jobs.

    It makes it simpler too see from the GUI too, from the Library level which/how many tapes are associated with which SILO copy.

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