file system size limits
Forwarded to the list.
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Sender: [email protected]
Message-ID: <[email protected]>
Date: Fri, 07 Jan 2000 11:58:05 +0100
Resent-Date: Fri, 07 Jan 2000 13:21:02 MEZ
From: Manfred Spraul <[email protected]>
To: "Theodore Y. Ts'o" <[email protected]>, [email protected]
CC: Andrea Arcangeli <[email protected]>, Andi Kleen <[email protected]>,
[email protected]
Subject: Re: file system size limits
[I added linux-LVM to the cc list because it could be a LVM problem]
Quoted 9 lines · Theodore Y. Ts'o
From: "Manfred Spraul" <[email protected]>
Date: Thu, 6 Jan 2000 20:08:59 +0100Ok, 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.
Quoted 6 lines
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].
Quoted 4 lines
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