[plug] Ubuntu woes

Daniel Pittman daniel at rimspace.net
Thu Jun 19 11:06:49 WST 2008

Steve Baker <steve at iinet.net.au> writes:

> Nothing out of the ordinary in the kern.log, messages, syslog,
> daemon.log, or the usual suspects in /var/log.
> All disks are in a hardware RAID - 8-port adaptec SATA-II raid card, 2
> discs in RAID-1 and 6 in RAID-5.  The two RAID-1 drives are 12 months
> or so old, the other 6 are all new.  My next plan is to find the
> afatools kit from Adaptec and run the afacli command to check the
> SMART status of the discs and then scrub (check) the arrays.
> What is confusing is some tasks are quite quick and others really
> slow.  Unpacking a tgz archive was quick, aptitude safe-upgrade takes
> a long time to do steps like read state information, build the tag
> database, etc. but the download was quick, then it took even longer to
> do the post-installation steps.

It sounds, to me, very much like your system is delivering good write
bandwidth[1] but terrible read bandwidth or latency.

Unpacking the tar is fast iff the content is in memory, but the update
is slow when it reads databases or faults in code from disk.  Network
runs at full speed, and the post-install was slow only where it had to
fault in code, etc...

At a guess.  Oh, are you running a vendor driver for the Adaptec card,
or is it all open source drivers?


[1]  ...or background writeout is masking the latency; is unpacking a
     tarball still fast if you run it as 'time { tar ...; sync; }'?

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