From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.redhat.com (ext-mx04.extmail.prod.ext.phx2.redhat.com [10.5.110.8]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id oA744Awf004119 for ; Sun, 7 Nov 2010 00:04:11 -0400 Received: from mail.spinn.net (mail.spinn.net [216.223.224.151]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id oA7440Ln027209 for ; Sun, 7 Nov 2010 00:04:00 -0400 Message-ID: <4CD6252A.9040003@spinn.net> Date: Sat, 06 Nov 2010 22:03:54 -0600 From: allan MIME-Version: 1.0 References: <4CD35D3E.5030200@cfl.rr.com> <4CD5F804.3040906@cfl.rr.com> In-Reply-To: <4CD5F804.3040906@cfl.rr.com> Content-Transfer-Encoding: 7bit Subject: Re: [linux-lvm] LVM + raid + san Reply-To: allane@spinn.net, LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: LVM general discussion and development Have you considered using mdadm for the RAID configuration and lvm to carve it up? Phillip Susi wrote: > My understanding of a SAN is where you get a few drive enclosures and a > few servers and plug them all into a sas expander so all of the servers > can see all of the disks. You seem to be talking about having all of > the disks on one server that then serves them over ethernet with iscsi. > I wouldn't want to do that because it adds a good deal of overhead to > the disk access and introduces a single point of failure. > > I'd rather just use LVM to manage all of the disks as part of a single > volume group so you can immediately transfer a lv from one server to > another, but I can't work out how to still manage to get raid without > having lvm do it with the dm-raid5 support. > > On 11/05/2010 12:39 AM, Stuart D. Gathman wrote: >> I would run LVM on the SAN server, exporting LVs as SAN units, and >> each host >> would get a virtual SAN disk to do with as it pleased, including running >> LVM on it. Then you don't have to deal with locking issues for a shared >> volume group. If your SAN server is embedded, it must already have >> some sort >> of management interface to parcel out disk space as virtual disks. >> If you don't like its interface, then consider replacing it with a >> general purpose host running LVM as described above. That said, many >> do use shared volume groups with no problem. >> >> Generally, your SAN (whether embedded or a dedicated general purpose >> host) >> already has the raid built in. The exported virtual disks are raid >> reliable. If not, replace the SAN. The whole point of SAN is to not >> worry about physical disks anymore on the client systems. If you had >> multiple >> SANs on separate physical LANs, you could stripe them for super speed, >> but >> otherwise raid is already built in. And you can bond multiple 1000BT >> interfaces with a gigabit switch to get really fast transfer from >> the SAN anyway. >> >> If the SAN server is a general purpose host, I would run raid10, or >> linux md >> extensions to it that get most of the benefits with fewer disks: >> >> http://en.wikipedia.org/wiki/Non-standard_RAID_levels >> >> raid5 has the read/modify/rewrite problem. >> >> I would not use the device-mapper raid, as you note. >> >> Caveat: I've never actually setup a SAN, just used them. >> > > _______________________________________________ > linux-lvm mailing list > linux-lvm@redhat.com > https://www.redhat.com/mailman/listinfo/linux-lvm > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ > >