From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Priebe - Profihost AG Subject: Re: Disabling journal Date: Mon, 12 Nov 2012 15:48:32 +0100 Message-ID: <50A10C40.9090909@profihost.ag> References: <50A019BE.9030002@profihost.ag> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail.profihost.ag ([85.158.179.208]:35223 "EHLO mail.profihost.ag" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751628Ab2KLOse (ORCPT ); Mon, 12 Nov 2012 09:48:34 -0500 In-Reply-To: Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Sage Weil Cc: ceph-devel@vger.kernel.org Am 12.11.2012 15:42, schrieb Sage Weil: > On Sun, 11 Nov 2012, Stefan Priebe wrote: >> Hi Sage, >> >>> With btrfs, yes, although this isn't something we have tested in a while. >> I'm not using btrfs as long as the devs claim it is not ready for prod. > > In that case, the journal is needed for consistency of the fs; we rely on > writeahead journaling. It can't be turned off. > > Putting it on a ramdisk in this case is interesting for performance, but > it means that a crash/reboot/powerloss event leaves the fs in an > inconsistent and unusable state. But only if for replicas 2 both nodes crash / have a powerloss? > The only time tmpfs is potentially useful in production is when you're > using btrfs *and* have independent backup power sources for replicas (and > can thus avoid worrying about a site-wide power failure and loss of > journal). (Or have relaxed requirements for the durability of recent > writes.) What happens for XFS and replicas two and ONE host has a power loss? The other replica / journal should be still there. I've no idea where to put the journal on. I mean i've 8 SSDs per Host one per osd each with a write IOP/s speed of 45.000 iops to whole IOP/s write speed of 360.000 IOP/s per Node. Which journal device can handle this? And if i put the journal on the same disk as the OSD it has to copy the data around. Greets, Stefan