Re: iostat - multiblock read count

From: Noons <wizofoz2k_at_yahoo.com.au>
Date: 25 May 2005 18:04:53 -0700
Message-ID: <1117069493.745577.8390@g49g2000cwa.googlegroups.com>

hopehope_123 wrote:

> 1. redhat linux advanced server ia64 , ocfs file system on emc
> raid10. + fibre channel ,
> no asyc , but direct_io active

I think I'm a bit in the blank here. How is direct_io active? By file system mount? If it is through Oracle, then a test of IO speed with "dd" in this case means you're writing to buffer cache, very very fast. Might as well use "hdparm -T <any raw device>" and see how fast you can write to buffer cache in one simple go?

Last time I looked, dd uses normal file system io if "of" is not a raw device. Which means we're merrily going through the buffer cache.

So what is the point of testing like this? Or am I missing something? Received on Wed May 25 2005 - 20:04:53 CDT