From mboxrd@z Thu Jan 1 00:00:00 1970 From: Heinz Mauelshagen Subject: Re: dm-cache: dirty state of blocks in writethrough mode Date: Tue, 23 Jul 2013 15:26:08 +0200 Message-ID: <51EE8470.6070302@redhat.com> References: Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============3408786159625775778==" Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: device-mapper development List-Id: dm-devel.ids This is a multi-part message in MIME format. --===============3408786159625775778== Content-Type: multipart/alternative; boundary="------------000409000702040600070803" This is a multi-part message in MIME format. --------------000409000702040600070803 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit On 07/23/2013 08:44 AM, Vijarnia, Anil wrote: > Hello, > In Documentation/cache.txt, section 'Updating on-disk metadata' mentions that "If the system crashes all cache blocks will be assumed dirty when restarted". > I am assuming that the above line is relevant for writeback mode only, and in writethrough mode the cache will always be coherent after a crash. > Can someone confirm/reject this assumption? That's correct Reason being that the cache never holds any dirty pages in writethrough mode. -- lvmguy > > Thanks > > > > > > > > -- > dm-devel mailing list > dm-devel@redhat.com > https://www.redhat.com/mailman/listinfo/dm-devel --------------000409000702040600070803 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit On 07/23/2013 08:44 AM, Vijarnia, Anil wrote:

Hello,
In Documentation/cache.txt, section ‘Updating on-disk metadata’ mentions that “If the system crashes all cache blocks will be assumed dirty when restarted”. 
I am assuming that the above line is relevant for writeback mode only, and in writethrough mode the cache will always be coherent after a crash. 
Can someone confirm/reject this assumption?

That's correct

Reason being that the cache never holds any dirty pages in writethrough mode.

-- lvmguy

Thanks

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