thanks for your response, Andreas.
It sounds like you have overflowed the end of the 2TB device limit and clobbered the beginning of your filesystem. This can happen if the SCSI driver, kernel, or even ext3 isn't handling offsets > 2^31 properly. I know RH has only recently started supporting ext3 filesystems > 2TB, and it isn't clear that all drivers handle this properly yet.
This box is using the fusion mpt drivers as in 2.6.7 - mptbase,mptscsih etc. Do you recall any >2Tb issue being fixed in later kernels? When the machine was last in a good state, the filesystem had 1.5Tbyte used, ie as far as I can tell nothing would have written past 2Tb, although I suppose there is no guarantee the space is used up in order of increasing offset. The filesystem was exported over NFS, and was being written to by client machines. It is using NFSv3 (nfs-kernel-server 1.0-2woody3). Worked great for several months.
Please update your e2fsprogs to the latest. You also need to use "e2fsck -b 32768" (or multiple thereof) for such large filesystems. I think newer e2fsprogs will print this message properly in that case.
I downloaded 1.38 from sourceforge and built it. No change in behaviour. I tried e2fsck with block offsets from 1025 to 4194305 in steps of 1024. I also tried dumpe2fs with the same range of offsets, also nothing. I've attached an strace of dumpe2fs, perhaps it is helpful? Another question. The e2fsck(8) manpage says the superblocks are at - Blocksize -b 1k 8193 2k 16384 4k 32768 Why is the superblock offset for 1k at 8193, not 8192? Is that an error in the manpage? Or should it be that the 2k, 4k block offsets should be odd, ie 16385, 32769? This article suggests the latter - http://www2.linuxjournal.com/article/0193
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