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From: Sage Weil <sage@inktank.com>
To: Tren Blackburn <tren@eotnetworks.com>
Cc: Gandalf Corvotempesta <gandalf.corvotempesta@gmail.com>,
	ceph-devel@vger.kernel.org
Subject: Re: Ceph journal
Date: Wed, 31 Oct 2012 14:54:37 -0700 (PDT)	[thread overview]
Message-ID: <alpine.DEB.2.00.1210311454080.20646@cobra.newdream.net> (raw)
In-Reply-To: <CANLRBoyLHrLP_hg6DSbESk=JhfHa5rzHiyLHcAotUokRe--xVA@mail.gmail.com>

On Wed, 31 Oct 2012, Tren Blackburn wrote:
> On Wed, Oct 31, 2012 at 2:18 PM, Gandalf Corvotempesta
> <gandalf.corvotempesta@gmail.com> wrote:
> > In a multi replica cluster (for example, replica = 3) is safe to set
> > journal on a tmpfs?
> > As fa as I understood with journal enabled all writes are wrote on
> > journal and then to disk in a second time.
> > If node hangs when datas are still on journal (and journal is not on a
> > permanent disk), some data lost could happens.
> >
> > In a multi replica environment, other nodes should be able to write
> > the same datas to disk, right? I this case, using a journal on a tmpfs
> > should be safe enough.
> 
> Unless you're using btrfs which writes to the journal and osd fs
> concurrently, if you lose the journal device (such as due to a
> reboot), you've lost the osd device, requiring it to be remade and
> re-added.

This is correct.  For non-btrfs file systems we rely on the journal for 
basic consistency.

sage

  parent reply	other threads:[~2012-10-31 21:54 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-10-31 21:18 Ceph journal Gandalf Corvotempesta
2012-10-31 21:24 ` Tren Blackburn
2012-10-31 21:32   ` Stefan Kleijkers
2012-10-31 21:54   ` Sage Weil [this message]
2012-10-31 21:58   ` Gandalf Corvotempesta
2012-10-31 22:04     ` Stefan Kleijkers
2012-10-31 22:07       ` Gandalf Corvotempesta
2012-10-31 22:55         ` Sébastien Han
2012-11-01 21:18       ` Gandalf Corvotempesta
2012-11-01 21:27         ` Mark Nelson
2012-11-01 21:33           ` Gandalf Corvotempesta
2012-11-03 17:29             ` Gregory Farnum
2012-11-04 11:48               ` Gandalf Corvotempesta
2012-11-05 13:06               ` Jean-Daniel BUSSY

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