(I sent this message on Feb 23, but it didn't appear on the list. I
resend it here without the logfiles attached. Maybe they were too
large.)
Hello,
I am trying to setup amvault for tape-to-tape duplication.
My problem is that the write speed is very low (about 12 MB/s) whereas
the native write speed usually is about 115 MB/s:
PART taper Set1K-2011-01 2 fileserver /backup 20120101030850 1/-1 0 [sec
16429.995803 bytes 208375369542 kps 12385.369628]
DONE taper fileserver /backup 20120101030850 1 0 [sec 16430.000000 bytes
208375369542 kps 12385.366464 orig-kb 310011210]
The amreport mail message finally says:
Avg Tp Write Rate (k/s) 14148.8 14148.8 --
USAGE BY TAPE:
Label Time Size % DLEs Parts
Set1K-2011-01 14:36 726591M 94.4 3 3
The tape drives ar IBM FC LTO-4, each connected to its own 4Gb FC
port. Running dd's to each drive in parallel I do not see a
bottleneck:
$ dd if=/dev/i500-lto4-tape1 bs=32k of=/dev/null bs=32k count=1000000
1000000+0 records in
1000000+0 records out
32768000000 bytes (33 GB) copied, 281.63 s, 116 MB/s
$ dd if=/dev/i500-lto4-tape2 bs=32k of=/dev/null bs=32k count=1000000
1000000+0 records in
1000000+0 records out
32768000000 bytes (33 GB) copied, 310.629 s, 105 MB/s
I tried to strace the processes/threads:
# ls -l /proc/21570/fd
total 0
lrwx------ 1 backup backup 64 Feb 23 14:07 0 -> /dev/pts/6
lrwx------ 1 backup backup 64 Feb 23 14:07 1 -> /dev/pts/6
l-wx------ 1 backup backup 64 Feb 23 14:07 10 ->
/var/log/amanda/server/MonthlySet1/amvault.20120223133643.debug
lrwx------ 1 backup backup 64 Feb 23 13:38 2 -> /dev/pts/6
lrwx------ 1 backup backup 64 Feb 23 14:07 3 -> anon_inode:[eventfd]
lrwx------ 1 backup backup 64 Feb 23 14:07 5 -> /dev/nst3
lr-x------ 1 backup backup 64 Feb 23 14:07 6 -> pipe:[5827058]
l-wx------ 1 backup backup 64 Feb 23 14:07 7 -> pipe:[5827058]
lrwx------ 1 backup backup 64 Feb 23 14:07 8 -> /dev/nst2
# ls -l /proc/21570/task/
total 0
dr-xr-xr-x 5 backup backup 0 Feb 23 13:45 21570
dr-xr-xr-x 5 backup backup 0 Feb 23 13:45 21573
dr-xr-xr-x 5 backup backup 0 Feb 23 13:45 21800
dr-xr-xr-x 5 backup backup 0 Feb 23 13:45 21801
My summary of whats going on (full logs attached below):
14:18:17.778803 the reader process starts reading 32k blocks
14:18:18.018007 the writer process starts writing
14:18:18.017894 the reader process doesnt show all the futex calls
14:18:18.285803 the writer stopps writing
14:18:18.295847 the reader stops reading
14:18:24.281473 the writer starts writing
14:18:24.281608 the reader starts reading
...
So ... something seems to be to slow so that the tape drives don't
keep streaming.
I am using Amanda 3.3.0 on Debian.
Any ideas, suggestions, ... ?
Thanks,
Sven
