Forum Discussion

Stiva's avatar
Stiva
Level 4
10 years ago

How to find maximum block size for tape device.

Hi All,

 

We have netbackup 7.1 installed on Solaris server. We are using LTO4 & LTO5 tapes for backup. I need a help to find the maximum block size for LTO4 & LTO5 tapes. Is there any way to find it out from netbackup end.

Some NDMP jobs are there in my environment and Data buffer size for NDMP is 64kb which reduce the backup throughput. I wanted to change it to 256kb for better performance but before that I wanted to check the maximum block size of tape.

Thanks in advance.

 

 

7.1.x and Earlier
Backing Up
Backup and Recovery
NetBackup
Solaris
  • mph999's avatar
    mph999
    10 years ago

    Max size is dependant on the tape drive itself, or HBA etc ... no way to tell from NBU without testing to see what works (backup and restore).

    However, the vast majority of people use 256k (262144 in SIZE_DATA_BUFFERS) along with 126 or 256 for the number of buffers.

    Have a look at this:

    http://www.mass.dk/category/netbackup-guides/

    Credit to Nicolai - it's his site but he gives a good explanation so I'm sure he won;t mind me posting it.

    Martin

  • Nicolai's avatar
    Nicolai
    10 years ago

    Direct NDMP where the device is writing its own data to tape, Netbackup is merely a control station and out of the data loop. Depending on the vendor (Neapp, EMC) and firmware revision, they may have a issue with other settings than the default. Best way to verify is look in the vendors documentation.

    If firmware revision of the NDMP device is relative new (+/ 2 year) I would not be worried.

    @Stiva: What kind of NDMP operation do you plan to use ?

    Some of the NDMP method is described in Netbackup NDMP admin guide 

    http://www.symantec.com/docs/DOC6456

    Despite the warnings, I still think its a good idea to change block size to 256K.

     Just taking little precaution before implementing any idea.

    This is also called "taking yore job serious" - credits for this from me :-)

  • sdo's avatar
    sdo
    Moderator
    10 years ago

    Whilst in some scenarios tape block size can be a NetBackup configurable element, really the maximum block size is an attribute of the tape drive itself and not NetBackup.  However, HBAs can have a maximum too.  And the HBA driver and/or tape drive driver can have maximums too.

    So, the true achievable maximum is the lowest of the highest values supported by tape drive and/or HBA and/or HBA driver and/or tape drive driver and/or NetBackup.

    Be careful though - you refer to NDMP - please describe your NetBackup for NDMP config?  Direct?  Three-way?  Remote?

  • sdo's avatar
    sdo
    Moderator
    10 years ago

    So, how to find the maximum?

    Research at least the five above elements... tape drive, HBA, HBA driver, tape drive driver, NetBackup.

    Choose a test value.

    Test backup, and you must test restore when changing tape drive block size.

    Beware the implications!  Do you want/need to restore at another site?  e.g. production site infrastructure may support a 256KB or 512KB tape block size - but the DR site might not!... and so, no restores at DR site!!

  • mph999's avatar
    mph999
    Level 6
    10 years ago

    Max size is dependant on the tape drive itself, or HBA etc ... no way to tell from NBU without testing to see what works (backup and restore).

    However, the vast majority of people use 256k (262144 in SIZE_DATA_BUFFERS) along with 126 or 256 for the number of buffers.

    Have a look at this:

    http://www.mass.dk/category/netbackup-guides/

    Credit to Nicolai - it's his site but he gives a good explanation so I'm sure he won;t mind me posting it.

    Martin

  • Marianne's avatar
    Marianne
    Level 6
    10 years ago

    Use robtest to mount a tape in a drive, then use nt_ttu  command to list parameters.

    See this TN (ignore the topic): http://www.symantec.com/docs/TECH22746 

    1. From the <install path>\Veritas\Volmgr\bin directory type the following command: 
    nt_ttu 
    nt_ttu> 
    2. At the nt_ttu> prompt, type "p" and press enter (without the quotes): 
    nt_ttu> p 
    This will list specific tape drive parameters.  
    3. Record the value for "maximum blocksize" 
  • Nicolai's avatar
    Nicolai
    Moderator
    10 years ago

    I would take a look at this tech note - but do test it very carefully. Not alle NDMP devices can do 256K block size.

    DOCUMENTATION: What is the SIZE_DATA_BUFFERS_NDMP tuning file?

    http://www.symantec.com/docs/TECH51967

    Thanks MPH999 for the reference :-)

  • Stiva's avatar
    Stiva
    Level 4
    10 years ago

    Thank you all for your replies.

    @Marianne : Given technote is for windows server. Will it work on Unix servers also?

    @Nicolai : I am confused here "Not alle NDMP devices can do 256K block size.". How do I get to know that which NDMP devices can do 256K block size. 

    I will try all suggetions provided here.

    I have just joined new organization, Just taking little precaution before implementing any idea... :) 

     

     

     

  • sdo's avatar
    sdo
    Moderator
    10 years ago

    Yes, 'robtest' should be applicable to any media server.

    .

    Take a look at the NetBackup Blueprint for NDMP, linked here:

    https://www-secure.symantec.com/connect/forums/list-netbackup-blueprints

    ...to first understand your NDMP config.

    Once you know which model of tape connectivity you have, this will reveal your options to you.

  • Stiva's avatar
    Stiva
    Level 4
    10 years ago

    Hi Sdo,

    Not about robtest. I am asking about command nt_ttu.

    I will check it tommarow and update you all.

    Thanks for NDMP blueprint. I will refer it.

     

     

     

  • Marianne's avatar
    Marianne
    Level 6
    10 years ago
    robtest can only be used on the robot control host to mount a tape. Sorry, I don't know if the command exist on *nix servers. I don't have access to a server to check, but I have never heard of a *nix or NDMP server with a problem with 256K block size.
  • Nicolai's avatar
    Nicolai
    Moderator
    10 years ago

    Direct NDMP where the device is writing its own data to tape, Netbackup is merely a control station and out of the data loop. Depending on the vendor (Neapp, EMC) and firmware revision, they may have a issue with other settings than the default. Best way to verify is look in the vendors documentation.

    If firmware revision of the NDMP device is relative new (+/ 2 year) I would not be worried.

    @Stiva: What kind of NDMP operation do you plan to use ?

    Some of the NDMP method is described in Netbackup NDMP admin guide 

    http://www.symantec.com/docs/DOC6456

    Despite the warnings, I still think its a good idea to change block size to 256K.

     Just taking little precaution before implementing any idea.

    This is also called "taking yore job serious" - credits for this from me :-)