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Noor_Toorabally's avatar
Noor_Toorabally
Level 4
11 years ago

Netbackup tuning guide, the size of shares data buffers UNIX

According the the Netbackup tuning guide, the size of shares data buffers UNIX should follow the following guideline:

64K for tapes
256K for disk

In a case where we have a VTL. I assume that the virtual tapes are considered as normal tapes for netbackup. So SIZE_DATA_BUFFERS is the value taken for the virtual tapes instead of SIZE_DATA_BUFFERS_DISK. But should virtual tapes not be treated as disks?

And if I consider to treat it as disk, the value I have to put would need to be 256K in the SIZE_DATA_BUFFERS. And then what if I need to set the value for real physical tapes?

Thank you in advance for considering my question. 

7.5
Backup and Recovery
Linux
NetBackup

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  • Nicolai's avatar
    Nicolai
    Moderator
    11 years ago

    Use 256K block size for tape as well. You are right about virtual tapes are considered normal tape for Netbackup

    NUMBER_DATA_BUFFERS/SIZE_DATA_BUFFERS are in play here.

    You can't tell Netbackup to treat a VTL as disk - Netbackup consider VTL as tape and handle it as such. After all Netbackup know it's writing to tape thru device driver (even if tape is emulated by a VTL)

    You use the same values for both VTL and physical tapes - but I can recall why you would use different values. Ually bigger scsi block sizes means less system overhead

    I did this test many years ago when LTO3 was hot but it still show what buffer tuning can do:

    Before tuning: 19MB/sec (default values)

    Second tuning attempt: 49MB/sec (using 128K block size, 64 buffers)

    Final result: 129MB/sec  (using 128K block size and 256 buffers)

  • Noor_Toorabally's avatar
    Noor_Toorabally
    Level 4
    11 years ago

    Thank you Nicolai and Stefanos, I am keeping the 256K value.

    The document Stefanos posted a very good one, thanks.