On Wed, 21 Sep 2005, Baldur Norddahl wrote:
I did not try spooling for two reasons. First is that the backup server only
has about 70 GB diskspace (two SATA disks in a mirror configuration). Many of
the servers have more data to backup than this, and the total backup set is
several times this. I got the impression that spooling only works if the
backup server has enough diskspace to hold all the data from a single client.
That's not correct, once the spool is full it's dumped to tape and then
the sequece restarts, This may sound ineffeicient, but it saves a lot of
wear and tear on fast tape drives by streaming data to the drive as fast
as it can run, avoiding "shoe shining" (tape constantly rewinding and fast
forwarding) which dramatically reduces a tape's throughput abilities.
Second, the disks can in the best case only deliver about half the raw write
speed of the tapestreamer. This is if the disks are not doing anything but
reading. But in the spooling case the disks would still be spooling data from
other clients, so I think I would get maybe 1/4 of the tapestreamers
potential with this method.
Why not get another drive just for spooling?
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