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Re: tape throughput - lto1
2006-07-06 11:18:22
On Thu, 6 Jul 2006 at 10:24am, Brian Cuttler wrote
I've added more work area to amanda, have been trying to find
what other problems we may be seeing with the job, since it
still seems to take longer than it should.
Upon looking more closely at the amanda report from amdump I see
that the tape I/O rate is around 1800 KP/s where as 2 months ago
15,000 was not unusual.
The reduction does not seem to be tied to a system reboot (patches,
installation of HBA [host bus adapter] for the LTO3) nor any other
event that I can identify, and in fact I notice that we seem to have
two step downs in the I/O rate, separated by aprox one tape cycle.
I'm going to assume that the drive is LTO1, since you say that twice (in
the subject, and in the part I snipped below) and LTO3 only once. :)
Based on some quick specs I found 16MB/s is native rate for LTO1, so your
15K above was normal.
My first suspicion would be that your DLE(s) outgrew your holding space,
so now they're dumping straight to tape over the network. But the amflush
you mention below would appear to speak against that.
I have tried to clean the tape drive, have tried to relabel the tape
(amflush running as I write) and will next try a brand new tape with
the assumption that the max number of tape cycles has been reached
on all volumes at the same time. While that would mean remarkable
quality control in manufacture, the tapes where all purchased at the
same time and have been used an almost identical number of times.
If the new tape doesn't help (I expect it will but who knows) I don't
know what else it might be, wear of the tape heads ?
Have you tested the tape performance outside of amanda? amflush *should*
go as fast as the tape and disk drives will let it, but it never hurts to
take as many things out of the equation as you can. Try 'dd'ing from
/dev/zero (or the Solaris equivalent) to the tape drive and see how fast
that goes. Ditto for tar with various block sizes.
The blocksize settings didn't get mucked up, did they?
If anything you do to the drive only goes at 1800KB/s, I'd say it's time
to call support. Did I hear the word Dell? *shudder* Good luck with
that (from a fellow Dell "user"). ;)
--
Joshua Baker-LePain
Department of Biomedical Engineering
Duke University
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