From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nat Makarevitch Subject: Re: the '--setra 65536' mistery, analysis and WTF? Date: Fri, 21 Mar 2008 15:12:13 +0000 (UTC) Message-ID: References: <18382.54925.354731.996508@tree.ty.sabi.co.UK> <18400.13488.178782.156775@tree.ty.sabi.co.uk> <18402.7274.174605.611654@tree.ty.sabi.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Peter Grandi lxra.for.sabi.co.UK> writes: > this seems to indicate that not only the Linux block IO subsystems issues > IO operations in multiples of the read-ahead size, but does so at a fixed > number of times per second that is a multiple of 10. Is it the case with a classic controller (not a 3ware?) http://forums.storagereview.net/index.php?showtopic=25923 may be of interest. > Which lead me to think about elevators, which was also mentioned > in some recent (and otherwise less interesting :->) Sorry, I don't understand this. > It still seems the case to me that the block IO subsystem > structures IO in lots of read-ahead sectors Isn't it specific to the 3ware driver and/or hardware, even in SINGLE (JBOD) mode? > Finally, I am getting a bit skeptical about elevators in general; > several tests show no-elevator as not being significantly worse > and sometimes better than any elevator Isn't it specific to intelligent controllers?