On Thu, 29 Jul 2004 at 11:10am, Narada Hess wrote

> I was having estimation timeout failures, so based on advice from this
> group (thanks), I increased the etimout value in amanda.conf from 600 to
> 6000. Yay, now my backups work! But I am frankly astonished at the fact
> that estimation took almost twice as long as the actual dump. Is this
> normal, or is there some way to speed this up?

That depends.  The estimate phase with tar (which from below is what I 
assume you're using) does tar cf /dev/null (among some other flags).  So 
it just stats the files, it doesn't actually read them off the disk.  This 
is generally *very* fast.  But if you have a case pathological to your 
filesystem (e.g. *lots* of very small files), it can be slowed down 
immensely.  If you look in the sendsize*debug file, you can figure out 
exactly how long each estimate is taking, and then examine that FS.

> Another concern is that the k/s rate is so slow. We are backing to an
> LTO-L1 drive which in normal use seems to run at about twice the
> reported speed. Does Amanda have a lot of overhead that is slowing
> things down? I guess I should do a straight gnu-tar dump and compare the
> transfer rates.

> Avg Dump Rate (k/s)      9949.6     9949.6        --
> 
> Avg Tp Write Rate (k/s)  9948.6     9948.6        --

Your dump and tape write speeds are the same, so you're not using a 
holding disk.  Holding disks can definitely speed things up.  Is the 
amanda server also the client?  If not, then what you're seeing is simply 
network speed.  If so, then, yes, do some benchmarking and make sure your 
disks can keep up with the tape drive.

-- 
Joshua Baker-LePain
Department of Biomedical Engineering
Duke University