From mboxrd@z Thu Jan 1 00:00:00 1970 From: Petro Subject: Re: [linux-lvm] multiple volumes.. Message-Id: <20020410002847.GE17367@auctionwatch.com> References: <18044083656.20020409231800@tnonline.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <18044083656.20020409231800@tnonline.net> Sender: linux-lvm-admin@sistina.com Errors-To: linux-lvm-admin@sistina.com Reply-To: linux-lvm@sistina.com List-Help: List-Post: List-Subscribe: , List-Unsubscribe: , List-Archive: Date: Tue Apr 9 19:28:02 2002 List-Id: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-lvm@sistina.com On Tue, Apr 09, 2002 at 11:18:00PM +0200, Anders Widman wrote: > I have a problem which I want to solve as efficiently as possible. > The problem is that I have 13 drives os various sizes (30-120GB) which > I want to combine into one (or a few) logical volumes with redundancy > if one drive would fail. > How would the smartest layout be? I was thinking about multiple > partiontions and then combine them into several RAID 5 chains, and > then use LVM to manage the logical volumes. The problem (off the top of my head) is that (1) this will give utter crap performance, and (2) If you're not *really* careful with your layout you could wind up losing a lot of data in a crash and (3) even if you don't loose data in a crash, a single drive fault will still drag performance into the toilet. > There is an expamle of my ideas at http://www.tnonline.net/raid-lvm.png > As you can see there are 8 chains and about 50 GB unallocated data in > this example. Can I minimize the loss even better? Using MD to make some meta-devices on the raw drive do: Stripe: 2x60 = 120 2x60 = 120 2x60 = 120 Raw: 120x1=120 Then layer these devices to become your initial RAID5 volume. That leaves 2x75, 2x80, 1x30, and 1x40: Linear mode the 30 and 40 to get 70, raid5 across these to get: 80 80 75 75 70 (30+40). This loses you about 30 gig. (10+10+5+5). If you really wanted you could recover that by working off partitions, but IMO it's just not worth it. -- Share and Enjoy.