From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Bryn M. Reeves" Subject: Re: Simulating faulty disk Date: Thu, 20 Oct 2011 16:56:25 +0100 Message-ID: <4EA044A9.6070406@redhat.com> References: <4E9F9321.8090704@cs.utah.edu> <4E9FE97E.4030209@redhat.com> <4EA04201.1050702@cs.utah.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mx1.redhat.com ([209.132.183.28]:50304 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753500Ab1JTP4e (ORCPT ); Thu, 20 Oct 2011 11:56:34 -0400 In-Reply-To: <4EA04201.1050702@cs.utah.edu> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Yathindra Cc: linux-scsi@vger.kernel.org On 10/20/2011 04:45 PM, Yathindra wrote: > Hi Bryn, > > Thanks for that info. Could you please tell me where I can find more > details about using it. > > Thanks again, > Yathi There's a couple of brief files describing the targets in the Documentation/device-mapper directory: http://www.kernel.org/doc/Documentation/device-mapper/dm-flakey.txt http://www.kernel.org/doc/Documentation/device-mapper/delay.txt They both work like the linear target (except that they introduce the specified faults according to their parameters). To set up a device with both you'd need to use a pair of stacked devices so something like: dmsetup create d0 --table="0 $SECTORS delay $DEVICE 0 500" dmsetup create f0 --table="0 $SECTORS flakey /dev/mapper/d0 0 9 1" This will create a device /dev/mapper/f0 that is drops out for 1s in every 10 and has a 500ms delay on reads and writes. SECTORS is the size of the underlying device in sectors (use e.g. $(blockdev --getsize)). You can optionally specify separate delays/device for writes to the delay layer and write loss / write corruption for the flakey layer - see the doc files and also the comments above flakey_ctr and delay_ctr for more details. Regards, Bryn.