From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <3A5355EF.2060207@liberate.com> Date: Wed, 03 Jan 2001 09:40:15 -0700 From: Chris Worley MIME-Version: 1.0 Subject: Re: [linux-lvm] Sanity check: newbie wants strange LVM configuration References: <3A52B71A.6944E0C5@symbionsys.com> <20010103093327.A619@66bassett.freeserve.co.uk> Content-Transfer-Encoding: 7bit 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: List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: linux-lvm@sistina.com Cc: joe@66bassett.freeserve.co.uk Joe, Good plan, but I have some questions... Joe Thornber wrote: > 6) turn the 12G drive into a PV > 7) extend the volume group with the new PV > 8) create a striped logical volume big enough to hold the 12G And LVM knows automagically to grab 12GB from the 40GB drive to stripe together into a 24GB drive? > OK so you should now have (40 - 6)G free on the big disk, and (12 -6)G > free on the smallest disk. Why don't I have 40-12 and 12-12 (nothing free on the smaller disk) resulting in a 24G raid0? Also, I think it would be better to do the 16G first, then the 12G. Is there any reason why you did the 12G first, or is this interchangeable? > 16) create a 16G striped LV Shouldn't this be a 32G striped LV (16G from the 16G drive, another 16G from the 40G drive)? > You now have a striped LV 12G, a striped LV 16G + lots of left over > extents that can be added when needed. Wouldn't that be a 24G striped LV and a 32G striped LV that I can append together into a 56G LV (and lots of non-striped extents that I can add to the end of that)? Thanks for your help, Chris > On Tue, Jan 02, 2001 at 10:22:34PM -0700, Chris Worley wrote: > >> I've got two disk drives, 12 & 16 GB IDE. I'm adding a third 40GB >> drive. Time to start using LVM... >> >> I want to get better performance, so, I'll put the 40GB drive on one >> IDE controller, the other two drives on the second controller. I'll >> make two partitions on the 40GB drive that match the disk sizes of the >> existing drives, and stripe each with it's match on the 40GB drive, >> creating two raid0 arrays (one 12+12, and the other 16+16). By >> placing the dual-partitioned 40GB drive stand-alone on one IDE >> controller, each striped with a partition/drive on the other >> controller, any given file will only be striped across one partition >> on each controller, so I should see the performance benefit of >> striping (on IDE). >> >> Should I use LVM or MD to do the striping (they both can do it, I was >> just wondering which would be a better choice)? >> >> Even if I use MD to stripe, I'd use LVM to append the two drives >> together. >> >> Before appending the drives, I'd make a temporary partition on the >> 40GB drive, and copy the current contents of the 16GB (/home) drive to >> the temporary partition. Then, I'd make the 16+16 raid0 a logical >> volume, create a reiserfs on it, and copy the information back from >> the temporary partition, to the new reiserfs. >> >> Since the 12GB drive is the current root partition, it's a bit >> trickier to copy. I'd copy it's contents to a temporary partition on >> the 40GB drive, boot from that temporary partition, then create the >> second 12+12 raid0, and add it to the first logical volume, then >> expand the reiserfs to cover both, copy the root file system from the >> temporary partition to the new logical volume, and setup a reiserfs >> root and boot. >> >> Is this the correct approach for upgrading? >> >> Finally, I'll have ~10GB unallocated on the 40GB drive. I was >> thinking of adding this to the end of the current logical volume (and, >> again, expand the reiserfs to cover the additional space). >> >> Since any file system looses performance when more than 90% full, this >> final non-striped partition would be in a position where performance >> would degrade anyway, and keep the raid0's in a position for full >> performance. >> >> Is that correct? >> >> Sort of off-topic (not LVM related)... >> >> I've got an IDE CDROM drive that I want to put on the same controller >> as the 40GB drive. I've been told that new UDMA drives do not have >> the PIO performance hit associated with CDROM drives, so I should be >> able to get full performance from my 40GB drive, even with a CDROM on >> the same IDE controller. >> >> Is that correct (or should I junk the IDE CDROM)? >> >> Thanks, >> >> Chris