SQL Server 2005 slow backup to UNC path
Posted on 2009-02-14
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.