[plug] Ubuntu woes

[Paul Antoine]

Those write speeds are ridiculously low... there's no way it should be 
that slow, even on RAID 5, especially given it's hardware RAID.

Are you running the 64-bit version on your machine? The normal kernel or 
the server version?

Paul

Steve Baker wrote:
> 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
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