Slow restore from tape

Last post 07-11-2018, 8:53 AM by efg. 3 replies.
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  • Slow restore from tape
    Posted: 07-10-2018, 10:07 AM


    My old backup (auxcopy) on tape (LTO5) have a very poor recovery speed for Windows NTFS File system (3GB/Hour). Whereas for SQL and Exchange it's very fast (380GB/Hour) from the same tape.

    Primary copies of these backups where on tape with a multiplexing of 3. No multiplexing and Combine to 1 streams on auxcopy. Any idea?


  • Re: Slow restore from tape
    Posted: 07-11-2018, 5:35 AM

    Hi Jetson

    You mentioned that your Aux Copy goes to Tape, however your "Primary copies of these backups where on tape with a multiplexing of 3"?

    If the primary concenr is Tape Restore performance, we will need to check the read speed from Tape (should be Clrestore) on the Client and the Write Speed to the Destination (CVD on the MediaAgent). 

    I would recommend to restore directly to the MediaAgent that has access to the Tape Library and see if the performance is better?

    The reason to restore directly to MediaAgent, is so you can bypass the need to write over the network, minimizing the variables.

    Hopefully the above helpts

    Thank you 


  • Re: Slow restore from tape
    Posted: 07-11-2018, 8:03 AM

    Hi Winston,

    Yes, at the time, Primary copies was on Tape with multiplexing of 3.

    Yes, the primary concern is Tape "restore" performance on Windows File System (NTFS), I never had a problem with the speed of backups. And also, I never had a problem with the speed of SQL or Exchange restore from the same Tape.

    I tried restore directly to the Media Agent that has access to the Tape Library and I have the same poor performance (~3GB/hour).

    Thank You for your help.


  • Re: Slow restore from tape
    Posted: 07-11-2018, 8:53 AM
    • efg is not online. Last active: 03-21-2019, 11:18 AM efg
    • Top 10 Contributor
    • Joined on 02-02-2010
    • CommVault Tinton Falls NJ
    • Expert
    • Points 1,616

    That may be the nature of the restore you are performing.   Remember that a tape is a sequential access device, and by nature SQL and Exchange DBs are typically made up of just a few large DB files where as a file system typically contains many files of varying sizes.   Now when it comes time for restore, the DB restore will be quick as the DB files will be read from the contiguous blocks that were written to the tape, but if restoring file system files...  those blocks may be scattered all over the tape, and so the mechanics involved in scanning the tape to access the desired blocks will slow down the process.  This is also known as "shoe shining" as the tape is scanned back and forth over the head to find the desired block of data.   (Which is why restoring from a disk based library can be much faster due to the random access capabilities of disk media).  What may help is if you perform a job based restore which should pull the data back off the tape in the same manner as which it was written which should increase the read speeds, but then if you don't really need to restore all the files from the incremental... (kind of a catch 22)  It's one reason that makes disk libraries more popular from a restore perspective...

    Ernst F. Graeler
    Senior Engineer III
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