On Wed, 31 Dec 2008, Greg Swift wrote:
> On Wed, Dec 31, 2008 at 17:35, Mike McGrath <mmcgrath@xxxxxxxxxx> wrote:
> On Wed, 31 Dec 2008, Corey Chandler wrote:
>
> > Mike McGrath wrote:
> > > Lets pool some knowledge together because at this point, I'm missing
> > > something.
> > >
> > > I've been doing all measurements with sar as bonnie, etc, causes builds to
> > > timeout.
> > >
> > > Problem: We're seeing slower then normal disk IO. At least I think we
> > > are. This is a PERC5/E and MD1000 array.
> > >
> >
> > 1. Are we sure the array hasn't lost a drive?
>
> I can't physically look at the drive (they're a couple hundred miles away)
> but we've seen no reports of it (via the drac anyway). I'll have to get
> the raid software on there to be for sure. I'd think a degraded raid
> array would affect both direct block access and file level access.
>
> > 2. What's your scheduler set to? CFQ tends to not work in many applications
> > where the deadline scheduler works better...
> >
>
> I'd tried other schedulers earlier but they didn't seem to make much of a
> difference. Even still, I'll get dealine setup and take a look.
>
> At least we've got the dd and cat problem figured out. Now to figure out
> why there's such a discrepancy between file level reads and block level
> reads. Anyone else have an array of this type and size to run those tests
> on? I'd be curious to see what others are getting.
>
>
> we are working on a rhel3 to 5 migration at my job. We have 2 primary filesystems. one is large database files and the
> other is lots of small documents. As we were testing backup software for rhel5 we noticed a 60% decrease in speed moving
> from rhel3 to rhel5 with the same file system, but only on the document filesystem, the db file system was perfectly
> snappy.
>
Our files are some smaller logs, but mostly rpms.
> After a lot of troubleshooting it was deemed to be related to the dir_index btree hash. The path was to long before
> there was a difference in the names of the files, making the index incredibly slow. Removing dir_index recovered a bit
> of the difference, but didn't resolve the issue. A quick rename of one of the base directories recovered almost the
> entire 60%.
>
I'd be curious to hear more about this. How long was your path? Our
paths aren't short but I don't think they'd be approaching any limits.
For example:
/mnt/koji/packages/nagios/3.0.5/1.fc11/x86_64/nagios-3.0.5-1.fc11.x86_64.rpm
> Thought I'd at least throw it out there, although I'm not sure that it is the exact issue, it doesn't hurt to have it
> floating in the background.
>
thanks.
-Mike
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