What does SQL Server's BACKUPIO wait type mean?
- by solublefish
I'm using Sql Server 2008 ("R1"), with some maintenance plans that back up my databases to a network share. Some of my backup jobs show long waits of type "BACKUPIO".
Of course it seems like this is an I/O subsystem limitation, but I'm skeptical. Perfmon stats for I/O on the production (source) server are well within normal trends for that server. The destination server shows a sustained 7MB/s write rate, which seems incredibly low, even for a slow disk. The network link is gigabit ethernet and nowhere near saturated.
The few docs I've turned up about BACKUPIO indicate that it's not specifically a wait on I/O, surprisingly enough. This MSFT doc says it's abnormal unless you're using a tape drive, which I'm not. But it doesn't say (or I don't understand) exactly what resource is missing.
http://www.docstoc.com/docs/24580659/Performance-Tuning-in-SQL-Server-2005
And this piece says it's not related to I/O performance at all.
http://www.informit.com/articles/article.aspx?p=686168&seqNum=5
"Note that BACKUPIO and IO_AUDIT_MUTEX are not related to IO performance."
Anyway, does anyone know what BACKUPIO actually means and/or what I can do to diagnose or eliminate it?
