Re: filer to SCSI-attached tape drive performance

On Thu, Oct 18, 2007 at 11:06:00AM -0500, John Foley wrote:

• is there a way to tell what the data rate to the tape drive is from the filer, over the SCSI bus ? I'm looking for more of an instantaneous measurement, rather than the overall average of (amount of data moved / time it took).

Are you looking at sysstat? It has a tape performance column.

• anyone else played around with this (ie, attempting to measure the data throughput from filer to SCSI attached tape drive) ? If so, what did you try, and what conclusions did you reach ?

What is the rate you're getting?

Is this with 'dump' or some commercial backup package? I might want to compare the speed between the backup package, just running a 'dump' on the same filesystem (will eliminate the production of catalog history data), and running a dump to the 'null' device. If the filer is under load, the tape drive may not be your bottleneck.