Re: Experiences with Ceph at the June'14 issue of USENIX ; login:

[Christian Balzer <chibi-FW+hd8ioUD0@public.gmane.org>]

Hello Filippos,

On Wed, 4 Jun 2014 17:22:35 +0300 Filippos Giannakos wrote:

> Hello Ian,
> 
> Thanks for your interest.
> 
> On Mon, Jun 02, 2014 at 06:37:48PM -0400, Ian Colle wrote:
> > Thanks, Filippos! Very interesting reading.
> > 
> > Are you comfortable enough yet to remove the RAID-1 from your
> > architecture and get all that space back?
> 
> Actually, we are not ready to do that yet. There are three major things
> to consider.
> 
> First, to be able to get rid of the RAID-1 setup, we need to increase the
> replication level to at least 3x. So the space gain is not that great to
> begin with.
> 
> Second, this operation can take about a month for our scale according to
> our calculations and previous experience. During this period of
> increased I/O we might get peaks of performance degradation. Plus, we
> currently do not have the necessary hardware available to increase the
> replication level before we get rid of the RAID setup.
> 
> Third, we have a few disk failures per month. The RAID-1 setup has
> allowed us to seamlessly replace them without any hiccup or even a clue
> to the end user that something went wrong. Surely we can rely on RADOS
> to avoid any data loss, but if we currently rely on RADOS for recovery
> there might be some (minor) performance degradation, especially for the
> VM I/O traffic.
> 
That. 
And in addition you probably never had to do all that song and dance of
removing a failed OSD and bringing up a replacement. ^o^ 
One of the reasons I choose RAIDs as OSDs, especially since the Ceph
cluster in question is not local.

Christian
-- 
Christian Balzer        Network/Systems Engineer                
chibi-FW+hd8ioUD0@public.gmane.org   	Global OnLine Japan/Fusion Communications
http://www.gol.com/