From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <3875DB88.8CF6C807@msede.com> Date: Fri, 07 Jan 2000 13:26:48 +0100 From: Michael Marxmeier Reply-To: manfreds@colorfullife.com MIME-Version: 1.0 Subject: [linux-lvm] Fwd: Re: file system size limits Content-Transfer-Encoding: 7bit Sender: owner-linux-lvm Errors-To: owner-linux-lvm List-Id: Content-Type: text/plain; charset="us-ascii" To: linux-lvm@msede.com Forwarded to the list. -------- Original Message -------- Sender: manfreds@colorfullife.com Message-ID: <3875C6BD.77A307DD@colorfullife.com> Date: Fri, 07 Jan 2000 11:58:05 +0100 Resent-Date: Fri, 07 Jan 2000 13:21:02 MEZ From: Manfred Spraul To: "Theodore Y. Ts'o" , linux-LVM@msede.com CC: Andrea Arcangeli , Andi Kleen , linux-fsdevel@vger.rutgers.edu Subject: Re: file system size limits [I added linux-LVM to the cc list because it could be a LVM problem] "Theodore Y. Ts'o" wrote: > > From: "Manfred Spraul" > Date: Thu, 6 Jan 2000 20:08:59 +0100 > > Ok, so the limits are even more complex: > * on an Alpha, you could build a 4TB ext2 volume and use it. > * if your Alpha crashes, and you connect your disks to an i386 box, then you > could corrupt your file system unless someone has added safety checks. > > I'm merely try to verify that these safety checks exist: > eg. ext2 on Alpha supports files > 2 GB, but linux-2.2 on i386 doesn't. If > you try to mount the disk on i386, then ext2 refuses to perform invalid > operations on these files. > > We're *way* ahead of you. I knew that, but this only means that ext2 is safe. What about the other subsystems? eg it seems that lvm doesn't contain the checks for lvm's > 2 TB on 32-bit platforms. * LVM can map up to 128 TB [I only checked the header file of LVM-0.8i] * This would work on 64-bit platforms. * If you attach these disks to a 32-bit platform, you'll corrupt your data. [but perhaps LVM will refuse to mount it, but I couldn't find such checks at first glance]. > The on-disk format of the ext2 filesystem only allows 4 bytes for the > block number, and it's defined to be an unsigned value. So if you're > using 4k blocks, the maximum theoretical filesize is 64 TB. (i.e., > 4*2^10*2^32 == 2^46) That's the ext2 limit. But the real-life limit is lowest value of (ext2-limit, ll_rw_blk limit, LVM limit, raid limit). I think we must check these limits, and ensure that everyone refuses to work with larger disks. ext2 is OK, but this doesn't mean that the complete chain syscall-to-disk will be OK. -- Manfred