James Harper wrote:

> I'd hazard a guess that for spooling, raw throughput is more important
> than random access seek time, unless you spool is fragmented.

You arte correct - IF you're only spooling one backup.

I may have anything up to 6 running simultaneously, some people on this 
list have much larger installations than mine.

As soon as you have more than one backup running there will be head seeks.

On a 4 spindle RAID-0 array, I found that aggregate throughput dropped 
more than 50% when spooling 2 100Gb files and unspooling 2 the same size.

Even just spooling one file while unspooling another had an aggregate 
performance hit of 25%.

On top of that the drives themselves tend to die quickly due to 
mechanical stress.

You won't see any of this if you're just spooling a single job, but in a 
largish installation with multiple tape drives and tens of terabytes of 
data, you _have_ to run simultaneous backups or you quite simply can't 
keep up.

AB




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