From: Andreas Dilger <adilger@dilger.ca>
To: "Loke, Chetan" <Chetan.Loke@netscout.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>,
Chris Mason <chris.mason@oracle.com>,
James Bottomley <James.Bottomley@HansenPartnership.com>,
Steven Whitehouse <swhiteho@redhat.com>,
Andreas Dilger <adilger@dilger.ca>, Jan Kara <jack@suse.cz>,
Mike Snitzer <snitzer@redhat.com>,
"<linux-scsi@vger.kernel.org>" <linux-scsi@vger.kernel.org>,
"<neilb@suse.de>" <neilb@suse.de>,
"<dm-devel@redhat.com>" <dm-devel@redhat.com>,
Christoph Hellwig <hch@infradead.org>,
"<linux-mm@kvack.org>" <linux-mm@kvack.org>,
Jeff Moyer <jmoyer@redhat.com>,
Wu Fengguang <fengguang.wu@gmail.com>,
Boaz Harrosh <bharrosh@panasas.com>,
"<linux-fsdevel@vger.kernel.org>" <linux-fsdevel@vger.kernel.org>,
"<lsf-pc@lists.linux-foundation.org>"
<lsf-pc@lists.linux-foundation.org>,
"Darrick J.Wong" <djwong@us.ibm.com>
Subject: Re: [Lsf-pc] [dm-devel] [LSF/MM TOPIC] a few storage topics
Date: Thu, 26 Jan 2012 10:00:04 -0700 [thread overview]
Message-ID: <10715842-8E51-40A5-8C28-AD8B1090645D@dilger.ca> (raw)
In-Reply-To: <D3F292ADF945FB49B35E96C94C2061B915A64111@nsmail.netscout.com>
On 2012-01-26, at 9:40, "Loke, Chetan" <Chetan.Loke@netscout.com> wrote:
> And 'maybe' for adaptive RA just increase the RA-blocks by '1'(or some
> N) over period of time. No more smartness. A simple 10 line function is
> easy to debug/maintain. That is, a scaled-down version of
> ramp-up/ramp-down. Don't go crazy by ramping-up/down after every RA(like
> SCSI LLDD madness). Wait for some event to happen.
Doing 1-block readahead increments is a performance disaster on RAID-5/6. That means you seek all the disks, but use only a fraction of the data that the controller read internally and had to parity check.
It makes more sense to keep the read units the same size as write units (1 MB or as dictated by RAID geometry) that the filesystem is also hopefully using for allocation. When doing a readahead it should fetch the whole chunk at one time, then not do another until it needs another full chunk.
Cheers, Andreas
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next prev parent reply other threads:[~2012-01-26 16:59 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20120124151504.GQ4387@shiny>
[not found] ` <20120124165631.GA8941@infradead.org>
[not found] ` <186EA560-1720-4975-AC2F-8C72C4A777A9@dilger.ca>
[not found] ` <x49fwf5kmbl.fsf@segfault.boston.devel.redhat.com>
[not found] ` <20120124184054.GA23227@infradead.org>
[not found] ` <20120124190732.GH4387@shiny>
[not found] ` <x49vco0kj5l.fsf@segfault.boston.devel.redhat.com>
[not found] ` <20120124200932.GB20650@quack.suse.cz>
[not found] ` <x49pqe8kgej.fsf@segfault.boston.devel.redhat.com>
[not found] ` <20120124203936.GC20650@quack.suse.cz>
[not found] ` <20120125032932.GA7150@localhost>
[not found] ` <F6F2DEB8-F096-4A3B-89E3-3A132033BC76@dilger.ca>
[not found] ` <1327502034.2720.23.camel@menhir>
[not found] ` <D3F292ADF945FB49B35E96C94C2061B915A638A6@nsmail.netscout.com>
[not found] ` <1327509623.2720.52.camel@menhir>
2012-01-25 17:32 ` James Bottomley
2012-01-25 18:28 ` Loke, Chetan
2012-01-25 18:37 ` Loke, Chetan
2012-01-25 18:37 ` James Bottomley
2012-01-25 20:06 ` Chris Mason
2012-01-25 22:46 ` Andrea Arcangeli
2012-01-25 22:58 ` Jan Kara
2012-01-26 8:59 ` Boaz Harrosh
2012-01-26 16:40 ` Loke, Chetan
2012-01-26 17:00 ` Andreas Dilger [this message]
2012-01-26 17:16 ` Loke, Chetan
2012-02-03 12:37 ` Wu Fengguang
2012-01-26 22:38 ` Dave Chinner
2012-01-26 16:17 ` Loke, Chetan
2012-01-25 18:44 ` Boaz Harrosh
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