From mboxrd@z Thu Jan 1 00:00:00 1970 From: Miles Fidelman Subject: Re: RAID6 and crashes (reporting back re. --bitmap) Date: Thu, 10 Jun 2010 18:40:11 -0400 Message-ID: <4C1169CB.1030903@meetinghouse.net> References: <4C1128C2.4020105@meetinghouse.net> <20100611005743.43664e5b@natsu> <4C11578B.8010202@meetinghouse.net> <20100611034108.6a2cdbc4@natsu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20100611034108.6a2cdbc4@natsu> Sender: linux-raid-owner@vger.kernel.org Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Roman Mamedov wrote: > On Thu, 10 Jun 2010 17:22:19 -0400 > Miles Fidelman wrote: > > >>> Do you currently have a write intent bitmap in the array? I think it can >>> reduce the need for recovery by an order of magnitude in some cases. Check >>> man mdadm for --bitmap if you don't use it yet. >>> >>> >> Just went through the process of turning it on for all my arrays. >> Incredibly painless and quick. Now I get to wait and see if it helps >> the next time I have a crash/reboot event. >> > I assume you went with "internal" bitmap, in which case if you notice that > write speed on the arrays became significantly lower, the first thing you > should look at is increasing the --bitmap-chunk size (I use 131072). > Now you tell me :-) Yes... went with internal. I'll keep an eye on write performance. Do you happen to know, off hand, a magic incantation to change the bitmap-chunk size? (Do I need to remove the bitmap I just set up and reinstall one with the larger chunk size?) > It is possible to use an external bitmap on an independent device (which has > almost zero performance impact), but in this case it could be non-trivial to > 100% ensure that such a device is mounted and accessible at the moment during > boot-up when md arrays are being started, especially if one of those arrays > also hosts the root FS. > I think I'll stick with internal. Thanks again, Miles -- In theory, there is no difference between theory and practice. In practice, there is. .... Yogi Berra