From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Haigh Subject: Re: Xen disk write slowness in kernel 3.8.x Date: Wed, 03 Apr 2013 22:42:10 +1100 Message-ID: <515C1592.1090102@crc.id.au> References: <515B8E7B.8070104@crc.id.au> <9F2C4E7DFB7839489C89757A66C5AD620899E9@LONPEX01CL03.citrite.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <9F2C4E7DFB7839489C89757A66C5AD620899E9@LONPEX01CL03.citrite.net> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Felipe Franciosi Cc: "Xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org On 03/04/13 22:36, Felipe Franciosi wrote: > Based on what you said later, your raid stripe size is 128KB. When you plug /dev/md3 to your guest, you will be going through blkback/blkfront which only support 44KB per request. This is interesting. The default size for a RAID5/6 via mdadm these days is 512Kb. > So can I ask what is the "task that is going on"? > I mean, what is your workload and how does it look like (in terms of reads/writes, (a)sync and size)? The load is mostly sequential writes. Samba + NFS shares mainly. Files are usually 300Mb -> 10Gb. Its mostly writes, with occasional reads. Interestingly, I get 220Mb/sec+ reads - but only ~50Mb/sec writes via the DomU. -- Steven Haigh Email: netwiz@crc.id.au Web: https://www.crc.id.au Phone: (03) 9001 6090 - 0412 935 897 Fax: (03) 8338 0299