[CentOS] IO causing major performance issues

Les Mikesell lesmikesell at gmail.com
Thu Nov 15 22:54:16 UTC 2007

redhat at mckerrs.net wrote:
> The specific issue I'm referring to at this point is on a system running
> mysql. All mysql data files are on a netapp filer but mysql's tmp directory
> is on local disk.  Whenever a lot of temp tables are created (and thus
> written and deleted from local disk quickly) we can't even log in to the
> machine - and our monitoring system gets all freaked out and we get
> lots of pages, etc... FYI this is two disks with hardware raid 1.
> Is it just me? Or is this specific to Dell systems, or is this just
> the state of the Linux kernel these days? Is there some magical patch
> I can apply to make this issue go away :)

Does the Dell have a raid controller?  I saw something like this long 
ago on a Dell with a raid card that appeared to queue up thousands of 
operations, then hit some kind of high water mark and stay busy 
(basically locking the system) for several minutes while it caught up. 
It seemed pretty fast as long as you never completely filled its 
queue...  These days I mostly run software raid1.

   Les Mikesell
    lesmikesell at gmail.com

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