From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Andreas Dilger Message-Id: <200102090005.f1905bc08799@webber.adilger.net> Subject: Re: [linux-lvm] questions In-Reply-To: <20010209003003.B29707@vestdata.no> from =?UNKNOWN-8BIT?Q?Ragnar_Kj=F8rstad?= at "Feb 9, 2001 00:30:03 am" Date: Thu, 8 Feb 2001 17:05:36 -0700 (MST) 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: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-lvm@sistina.com Ragnar Kj_rstad writes: > On Thu, Feb 08, 2001 at 03:44:33PM -0700, Andreas Dilger wrote: > > Yes, even LVM has the 2TB limit at this point. This is because LVM > > presents itself to the rest of the kernel as a block device (just like > > any other), so the kernel 2TB limit for block devices still holds. > > For the volume, but not for the diskgroup, right? Yes, the 2TB limit is for a single LV. You can have up to 255 LVs in total I think, so 512TB total usable space with LVM, assuming your configuration works in this way. Probably the 255 LV limit will be a problem before the 512TB limit is... > > Heinz talked about allowing LVM to have PAGE_SIZE (4k) blocks (unlike > > the rest of the kernel, which uses 512 byte blocks) so it may be possible > > to go up to 16TB with LVM without a huge amount of kernel redesign. > > This sounds really interesting. What exactly would be needed to do that? Change all of the code paths in the kernel that assume block size is 512 bytes... > I believe there have been issues with lvm block sizes and XFS (maybe > other filesystems too). Would changing it to 4k create new issues? Yes, probably. > Would it be possible to increese it even futher? if the filesystem used > more than 4k blocksize? Probably not. There will likely be lots of problems for block size > PAGE_SIZE. Of course on ia64 and alpha PAGE_SIZE = 8kB, so you can go to 32TB I think, assuming the rest of the issues are fixed. Cheers, Andreas -- Andreas Dilger \ "If a man ate a pound of pasta and a pound of antipasto, \ would they cancel out, leaving him still hungry?" http://www-mddsp.enel.ucalgary.ca/People/adilger/ -- Dogbert