[linux-lvm] Fwd: Re: file system size limits
mike at msede.com
Fri Jan 7 12:26:48 UTC 2000
Forwarded to the list.
-------- Original Message --------
Sender: manfreds at colorfullife.com
Message-ID: <3875C6BD.77A307DD at colorfullife.com>
Date: Fri, 07 Jan 2000 11:58:05 +0100
Resent-Date: Fri, 07 Jan 2000 13:21:02 MEZ
From: Manfred Spraul <manfreds at colorfullife.com>
To: "Theodore Y. Ts'o" <tytso at MIT.EDU>, linux-LVM at msede.com
CC: Andrea Arcangeli <andrea at suse.de>, Andi Kleen <ak at muc.de>,
linux-fsdevel at 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" <manfreds at colorfullife.com>
> 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
* LVM can map up to 128 TB [I only checked the header file of
* 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
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
work with larger disks.
ext2 is OK, but this doesn't mean that the complete chain
syscall-to-disk will be OK.
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