[plug] Ubuntu woes

[Steve Baker]

Patrick Coleman wrote:
> You're not running LDAP on it, are you? I've seen similar issues with
> machines that are bound to LDAP (/etc/nsswitch.conf) but can't contact
> the LDAP server.
>
> The other thing to look for might be an NFS mount that can't contact the server
Interesting thought, however - no.  No mention of ldap in nsswitch.conf, 
and this system doesn't have any NFS mounts on other servers (although 
it is an NFS server itself).

I would think that the really slow boot (took nearly 20mins tonight when 
I restarted with upgraded kernel) is a key symptom.

I checked the RAID during reboot, both arrays are optimal (neither are 
degraded).

Timing for writing and then reading 100MB and 1GB files to each RAID are 
as follows (/tmp is on the RAID-1 and /home is on the RAID-5)

(Apologies here for the long stream of data... summary: writing/reading 
100MB and 1GB files, write speed 5.9-6.6 MB/s, read speed 60-116 MB/s)

root at eclipse:/tmp# time (dd if=/dev/zero of=/tmp/testfile bs=1M 
count=100; sync)
100+0 records in
100+0 records out
104857600 bytes (105 MB) copied, 16.0295 s, 6.5 MB/s

real    0m17.397s
user    0m0.590s
sys    0m16.470s

root at eclipse:/tmp# time (dd if=/dev/zero of=/home/testfile bs=1M 
count=100; sync)
100+0 records in
100+0 records out
104857600 bytes (105 MB) copied, 17.6852 s, 5.9 MB/s

real    0m19.172s
user    0m0.580s
sys    0m17.960s

root at eclipse:/tmp# time (dd if=/dev/zero of=/tmp/testfile bs=1M 
count=1000; sync)
1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 158.052 s, 6.6 MB/s

real    2m39.904s
user    0m0.650s
sys    2m38.590s

root at eclipse:/tmp# time (dd if=/dev/zero of=/home/testfile bs=1M 
count=1000; sync)
1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 169.352 s, 6.2 MB/s

real    2m51.243s
user    0m0.630s
sys    2m49.540s

It's not uncommon for RAID-5 to be slightly slower on writes than 
RAID-1, at first glance these throughput rates don't look too far off 
what you'd expect for sustained transfer rates (for a single drive, 
anyway).  Is that right?

Read times shown below are significantly better as you would expect.  
It's faster off the RAID-5 I guess because it is striped across 6 drives 
instead of 2:

root at eclipse:/tmp# echo 3 > /proc/sys/vm/drop_caches

root at eclipse:/tmp# time dd if=/tmp/testfile of=/dev/null bs=1M count=100
100+0 records in
100+0 records out
104857600 bytes (105 MB) copied, 1.73185 s, 60.5 MB/s

real    0m2.454s
user    0m0.330s
sys    0m1.010s

root at eclipse:/tmp# time dd if=/home/testfile of=/dev/null bs=1M count=100
100+0 records in
100+0 records out
104857600 bytes (105 MB) copied, 1.18612 s, 88.4 MB/s

real    0m1.563s
user    0m0.340s
sys    0m0.820s

root at eclipse:/tmp# echo 3 > /proc/sys/vm/drop_caches

root at eclipse:/tmp# time dd if=/tmp/testfile of=/dev/null bs=1M count=1000
1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 12.7445 s, 82.3 MB/s

real    0m13.107s
user    0m0.370s
sys    0m6.180s

root at eclipse:/tmp# time dd if=/home/testfile of=/dev/null bs=1M count=1000
1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 9.00243 s, 116 MB/s

real    0m9.695s
user    0m0.380s
sys    0m6.320s

Read performance seems to be fine, write speed seems a little slow but 
not enough to cause the sort of performance issues I seem to be 
experiencing.

Does this give anyone else any other ideas?  I greatly appreciate all 
the tips received so far.

Regards,
Steve