SQL Server 2005 slow backup to UNC path

Posted on 2009-02-14
Last Modified: 2012-05-06
I occasionally watch SQL Server 2005 database backup network performance with the Networking tab in Task Manager, in an attempt to estimate if the backup will take a little time or a lot of time (minutes or hours, basically).  The backup runs from one server connected to the SAN to another server connected to the SAN (same SAN or different...not certain it makes a difference).  The destination is a server with either a hidden share in the path, or a visible share on the network (again, doesn't seem to make a difference).  All target paths are full UNC.  When running a SQL Server 2005 backup using standard SQL commands in a SQL Agent job, the backup will perform in any of three different scenarios:
- Start out with network utilization in double digits (10-30%, depending on other activities on the network), then drop off into less than 5% for the remainder of the backup.  This is the most common scenario.
- Wide swings of network utilization almost continuously.  I've seen this run with as high a variance of 60+%, with the low point being 1% or less.
- A steady utilization throughout the entire job, generally in the double-digit range.  This appears to be elusive...only seen it a few times.

Theoretically, what would cause the wide swings of network utilization?  What would cause the backup to start out in turbo mode and drop off badly afterward?  This is a significant issue because backups invariably fail with an error message "The specified network name is no longer available."  This occurs almost nightly.

Question by:ejohnson4211
    LVL 63

    Expert Comment

    1) try with a mapped drive instead

    2) What is CPU usage during the backup ?

    3) Is there anyting else running that can cause network bottlenecks ( other backups ?? )

    I hope this helps !

    Author Comment

    1) I'll suggest the mapped drive idea to the network admins, thanks!  What is the difference overall between the two approaches?
    2) CPU is hardly a trickle usually...10% or less maybe.
    3) The network is highly utilized in the company I'm currently working at.  But I've seen this behavior at other companies as well, so I can no longer ascribe it to other activity.

    Here's the other thing that is unusual about this problem:  The profiles I mentioned earlier seem to have affinities to specific servers.  That is, of the two less-than-ideal scenarios listed previously, that same one will occur almost always for a given server.  I've run backups simultaneously among several servers, all hitting the same place, and watch them in the Network tab of Task Manager to find them operating differently on each server.  When I start up another backup on the same server where one just finished, it will have the same profile as its predecessor.
    LVL 57

    Expert Comment

    by:Raja Jegan R
       You cant use Mapped Drives for Backup and Restore in SQL Server as SQL Server cannot read mapped drives. In your backup and restore commands you always have to refer the network drive or network share using UNC path.

    UNC path has the following format: \\MachineName\ShareName or \\MachineName\DriveLetter$\Path

    << Start out with network utilization in double digits (10-30%) , high a variance of 60+% >>

    Yes it would be. Because as your data is moving to a network path and based on your network bandwidth and sharing this may vary.

    Kindly run Perfmon on the server which has that network share and find out the File I/O, Read Counters, Write Counters and other disk storage statistics.

    I suspect some problem in writing files in your network share more than the network bandwidth.

    And one of my another suggestion is Back up the Database to a different SAN if possible.
    LVL 57

    Expert Comment

    by:Raja Jegan R
    << The specified network name is no longer available >>

    This can be resolved in any one of the approaches:

    1. Open the firewall on the destination machine for this machine.
    2. Check whether Computer Browser Service in your Network share server is running.
    3. Or You may be using Symantec Endpoint Protection in your machine. If Yes, this is a known issue as per Symantec and a fix is available:

    Author Comment

    Thank you rrjegan17 for your comments.  I will follow up with Networks Services when I'm onsite later this week and post results or additional findings.

    Accepted Solution

    It appears the issue was with the cache card on the SAN.  The cards were installed and charged (not certain yet what that means) and I'm running a test backup now.  Network utilization is running about 9-15%...better than before, but may not still be up to par.  When the backup finishes, I'm going to compare performance with a backup I took yesterday that was pointed to the previous target server.

    Likely I will close this out tomorrow.  Thanks!
    LVL 57

    Assisted Solution

    by:Raja Jegan R
    Ok.. Then I have one more suggestion out for you:
    To confirm whether this is a problem with your cache or in the disk, run perfmon test on both the server machine and the destination server where your backup is stored. check this one out

    Hope above perfmon tests will help you to narrow down to your exact issue.

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