slow backup rate on 120T (DDS4 autoloader)

John Crowley jcrowley at
Wed Jun 12 11:30:00 CDT 2002

I have a PowerEdge 6400 running Red Hat 7.2.  The main user-data
partition on this system is approximately 11gig.  

I've got mtx installed for moving around the tapes in the autoloader. 
To run a test I am using a simple dump as follows:
/sbin/dump -0u -f /dev/nst0 /dev/sdb1

However, for the first 20 or so minutes of backup, the speed is 200
kb/sec.  This slowly increases over 8 hours to get up to about 320
kb/sec.  At this point in the night, something hangs the backup process.
 I'm trying to pinpoint when, but this being a production machine,
nothing really is running, and no major cron jobs.  (it's slow
troubleshooting something once a day)
I tried turning off compression to see if this sped it up.  No change. 
System has 2gig mem, and plenty of swap free... backups seem to use a
lot of CPU time but that's it.

On another system with a similiar setup I'm backing up 1.5 gig of data
in an hour with this same setup.  

I have amanda installed, and used it, and it had similiar slowness
(doing basically the same thing) which is why I fell back to straight
dump for testing.

Is this tape drive just painfully slow?  I can handle doing incrimentals
on weekdays and fulls on weekends, but I'll have to track down why the
dump is hanging to manage this.  Still, this seems much slower than it
should be.

Any ideas?  I'm not subscribed, but I've looked thru all the archives
(here and elsewhere).  I have an arcserve CD that I've been thinking of
installing to see if it backs up slowly as well, but from what I've read
arcserve needs apache setup via rpm, which isn't the case on this

oh, kernel  2.4.7-10smp

John Crowley
Unix Systems Administrator
Smith College

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