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Mohmec's avatar
Mohmec
Level 4
12 years ago

WAN latency requirements from the master to media servers

What is the wan latency requirements from the master to media servers when Master is at DR site and media at primary site?

There is frequent communication between the Master and Media Servers during a backup. So I think the speed of the backup depends on speed of communication between master and media server. So it may cause the backup slow down if the data can not be written quickly enough to the Master.

 

  • Here is the technote http://www.symantec.com/docs/HOWTO56209

    It says:

    For MAX_FILES_PER_ADD, try a number that is larger than the 5,000 default. A larger number may improve backup performance, particularly when the connections between media servers and the master server are slow.

6 Replies

  • Yes and no ... There is communiction between the master and media yes, but really it is only the file metadata, or in otherwords, what ends up in the NBU catalog. So considering 1 master and 1 media server, the speed of the backup is not going to be limited by the speed of the backup between the two servers. I suppose you might ask, what if you had many media servers - well, I've never seen enough media servers backing up clients at the same time, where the speed of the backups has been idenified as a problem due to the network speed between the master and media servers. Martin
  • Thanks Martin. But in a scenario where in we have catalog size more than 750GB and many media servers, I wanted to make sure the latency limits if any. for example, should it be less than ~100?  It seems to me a local Master may a better option, but need to understand the details before I propose a change.

  • The size of the catalog makes no difference. I managed to miss the DR site bit, so remote master - my previous answer, I was thinking local ... I don't have any answers off the top of my head, I think others will be along so who may. A quick answer may be to run AppCritical between the master / media(s) - NBU support could help with this. Other idea is to see if there are delays between bpbrm and bpdm in sending the catalog updates. M
  • >What is the wan latency requirements from the master to media servers when Master is at DR site and media at primary site?

    There is no any, unless your backups are failing.

    For example, if your system is not able to update the catalog within 10 minutes then the job will fail.

    >There is frequent communication between the Master and Media Servers during a backup.

    Are you sure? If the client is actually trasfering the data to the media, then there is just an idle session between master and media (that's why we usually worry about keepalive setting).

    During backups, data transfer between master and media happens only when the system needs to update the catalog. But that is just a metadata. And much bigger problem is not network latency but emm response time (sometimes master servers are just overloaded).

    >So I think the speed of the backup depends on speed of communication between master and media server. So it may cause the backup slow down if the data can not be written quickly enough to the Master.

    The only situation, I may think of, is if you're backing up millions of small files. That may cause massive catalog updates and delays.

    You may try tuning MAX_FILES_PER_ADD. Default value is 5000 (if I remember that right) and it could be recommended to increase the value for slow or overloaded connections between master and media.

  • Here is the technote http://www.symantec.com/docs/HOWTO56209

    It says:

    For MAX_FILES_PER_ADD, try a number that is larger than the 5,000 default. A larger number may improve backup performance, particularly when the connections between media servers and the master server are slow.