From mboxrd@z Thu Jan 1 00:00:00 1970 From: Petro Subject: Re: [linux-lvm] Problems and questions with LVM on a large raid system. Message-ID: <20030312234520.GA19335@auctionwatch.com> References: <20030312195217.GC18876@auctionwatch.com> <20030312221320.GA15196@gw.silicide.dk> Mime-Version: 1.0 Content-Disposition: inline In-Reply-To: <20030312221320.GA15196@gw.silicide.dk> 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: Wed Mar 12 17:46:02 2003 List-Id: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-lvm@sistina.com On Wed, Mar 12, 2003 at 11:13:20PM +0100, jon+lvm@silicide.dk wrote: > On Wed, Mar 12, 2003 at 11:52:17AM -0800, Petro wrote: > > I've got a couple of brand new boxes I'm trying to get LVM set up > > properly on. > > These machines have 6 200GiB drives attached to a 3ware controller card, > > for a total of 1,200,000,000,000 bytes of storage. > later down you write you need speed. In that case i would suggest > ditching the hardware raid, and use pure software raid, it is faster. > I dont mind 3ware, i have dome myself, but my benchmarking revealed > that software was faster. The production data we gathered showed the opposite--at least for the 3ware cards in our environment (we had about 5-8% more overhead running the 3ware cards RAID0 than we did running either raw disk (cheap IDE cards) or having the 3ware card pretend to be a jbod. This wasn't benchmarking, this was set it up and throw it over the wall for a month or two and see what the numbers looked like. A really nervous way of testing. > > I'm running kernel 2.4.18, with LVM version 1.0.3, and the lvmtools > > version 1.0.1rc3-1 (long story, but upgrading is a path-of-last-resort). > if you need snapshots, get 1.0.7 If I get the chance I'm probably going to ditch LVM since I don't need snapshots. I initially was give snapshots as a requirement. Unfortunately I'll probably not get a chance to redo these. > > Initially I had the drives set up as a single raid0 device, but doing a > > pvcreate on it failed with a message that said something about "can't > > get size". > strange, linux should be able to handle 2T block devices. Yes. It should. But when I did a pvcreate /dev/sda, where sda was 6 drives in a raid0, it failed. > > So I set up 2 3 disk RAID0 devices, and did a vgcreate /dev/sda /dev/sdb. > > Now, one question I have is: > > Does this concatenate the devices, or does it interleave the > > devices? IE do I have a stripe of stripes, or two stripes? > that depends. You can stripe the lvm, but then you cant resize it. > if you made a LV, then it would proberly just allokate all on one > "disk", aka sda, and then on sdb. I'm using 100% of the VG for the same LV. I'm fine with not being able to resize it. Do I need the MD stuff to stripe it? > > Since I need the disk write rate of all 6 drives, I'm *REALLY* hoping > > that it's interleaved. > sorry... it is not interleaved. > JonB > ps: how big a partition do you need stripping for? Do you need the > advanced LVM stuff, like resize, snapshot... I need slightly over 1T of formatted disk space on each system. Which means i really need to find a way to send an through an ssh session to a telnet window. -- "On two occasions, I have been asked [by members of Parliament], 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?' I am not able to rightly apprehend the kind of confusion of ideas that could provoke such a question." -- Charles Babbage