From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Nelson Subject: Re: TIER: combine SSDs and HDDs into a single block device Date: Thu, 02 Aug 2012 12:02:44 -0500 Message-ID: <501AB2B4.2010406@inktank.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ob0-f174.google.com ([209.85.214.174]:54715 "EHLO mail-ob0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754457Ab2HBRCr (ORCPT ); Thu, 2 Aug 2012 13:02:47 -0400 Received: by obbuo13 with SMTP id uo13so14086264obb.19 for ; Thu, 02 Aug 2012 10:02:46 -0700 (PDT) In-Reply-To: Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Tommi Virtanen Cc: ceph-devel@vger.kernel.org On 8/2/12 11:13 AM, Tommi Virtanen wrote: > Sounds like bcache in writeback mode. Assumes all underlying block > devices are RAIDed, or losing one will mean losing data; that is, for > example RAID1(SSD+SSD) & RAID5(8*HDD). > > http://www.lessfs.com/wordpress/?p=776 > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Neat! I'll try to play with it once the test hardware all makes it in. Alex is also trying to bug the XFS guys (and Sage bugged the BTRFS guys) about ways to put metadata on SSD while keeping data on spinning disk. It sounds like there is a hack for XFS that would let us keep inodes in the lower portion of a volume up to some configurable boundary and then we could use lvm to assign that portion of the volume to an SSD. The BTRFS guys have a SOC project in the works to separate out metadata onto another disk. I think these kinds of things could really help our small request performance. Mark