Re: iostat - multiblock read count

Fabrizio wrote:

> Is this a Redhat limit?

AFAIK, yes. That's why it is in the RedHat Bugzilla. It's not really a limit: just a default design decision of the 2.4 kernel people, I guess. And only for 2.4 kernel level. Ie, supposedly fixed in RHAS4 which is kernel 2.6 (or so I'm told...).

And of course in SLES 9 onwards? But then again, SLES always traditionally seemed to have less restrictions than RH. Looking at the compatibility tables in Metaclick for asynchIO and directio for different flavours of Linux, it comes out very clearly SLES paid attention to this disk stuff a lot more than RH. And it also supports a lot more file systems... (but I'm biased towards Suse, so take this with a grain of salt!)

>
> 40960.00 K / 322 = 127.20 K
>
> almost 128 K which can be the limit of my physical device.

Yeah. I think the patch lets it go to 1M which is what you need for sequential IO in devices like the low-cost RAID stuff Oracle is looking at now.

> (by the way: redhat bug 148838 speaks about a 128K limit on qlogic).

Yup, very much so. Which happens to involve all disk IO. See the best practices pdf link posted before for details. Received on Tue May 24 2005 - 21:14:18 CDT