On Wed, 31 Dec 2008, Corey Chandler wrote:I can't physically look at the drive (they're a couple hundred miles away)
> 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?
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.
I'd tried other schedulers earlier but they didn't seem to make much of a
> 2. What's your scheduler set to? CFQ tends to not work in many applications
> where the deadline scheduler works better...
>
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.
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%.
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.
-greg/xaeth
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