I know this is no answer, so apologies in advance.

Why are you worried about restore speeds? Hopefully you will never need
it and if you do, will anyone really complain that it took a little
longer than the tape drive is capable of? My users are usually just
grateful that they can get anything back. Plus, if I'm too quick,
they'll ask more and more often :)

JLM



> -----Original Message-----
> From: owner-amanda-users AT amanda DOT org [mailto:owner-amanda-
> users AT amanda DOT org] On Behalf Of Ryan Steele
> Sent: Tuesday, December 18, 2007 1:16 PM
> To: amanda-users AT amanda DOT org
> Subject: Discrepancy between amrestore and dd speeds
> 
> Hello list,
> 
> I've been performance testing Amanda, trying to get the setup ready
for
> prime-time, but I'm having an issue getting my read speeds from tape
to
> get even to 6MB/s.  My writes are about 12.7MB/s, which is what the
> tape
> drive boasts (12-24MB/s normal and 2:1 compression, respectively).
> But,
> my reads seem to hover around 5.5MB/s.  I ran some dd tests, which
show
> the data being pulled off at 11.7MB/s, and I'm not quite sure how to
> tell what amrestore is doing that is causing the performance drop off.
> Here are the tests I ran; any help is appreciated.
> 
> backup@amandaserver# dd if=/dev/nst0 of=/home/restores/foobar bs=256K
> count=10000G
>                                        10308+0 records in
>                                        10307+0 records out
>                                        2701918208 bytes (2.7 GB)
> copied,
> 230.539 seconds, 11.7 MB/s
> 
> 
> backup@amandaserver# amrestore -r /dev/nst0 hostname /foo/bar
> 
> backup@amandaserver# stat
> /home/restores/hostname._foo_bar.20071216.0.1.RAW
>                                        File:
> `home/restores/hostname._foo_bar.20071216.0.1.RAW'
>                                        Size: 2836922368      Blocks:
> 5546275    IO Block: 131072 regular file
>                                        Device: 908h/2312d      Inode:
> 13          Links: 1
>                                        Access: (0640/-rw-r-----)  Uid:
> (   34/  backup)   Gid: (   34/  backup)
>                                        Access: 2007-12-18
> 12:50:15.000000000 -0500
>                                        Modify: 2007-12-18
> 12:58:40.000000000 -0500
>                                        Change: 2007-12-18
> 12:58:40.000000000 -0500
> 
> So,  ~8 minutes for a 2.7GB file = ~5.7MB/s.  I saw similar
performance
> when retrieving a DLE that spanned 6 chunks (~5.3MB/s)  No errors or
> anything in my amrestore logs, just start and stop times.  I'm kind of
> at a loss as to what would be causing this, unless my calculations (
> size / time ) aren't valid?  Thanks.
> 
> Best Regards,
> Ryan
> 
> --
> Ryan Steele
> Systems Administrator
> The Archer Group