Hi everyone,
I'm having a problem with data corruption using devmapper on a SATA
disk using sata_sil24. I've done some work tracking it down, and
hopefully you folks can point me further in the right direction.
The kernel I'm using is 2.6.21-1.3228.fc7 (i.e. Fedora 7). LVM2 is
lvm2-2.02.24-1.fc7. The dmsetup and libdevmapper is
device-mapper-1.02.17-7.fc7.
The original setup that showed the problem is this:
Starting with two 500GB SATA drives (interface card uses a Silicon
3124 chipset), /dev/sdd and /dev/sde. I partitioned each into two
250GB chunks (250*1000*1000*1000, not 250*1024*1024*1024), and set up
two RAID 1 sets such that /dev/md0 is /dev/sdd1+/dev/sde1 and /dev/md2
is /dev/sdd2+/dev/sde2. I then created a volume group ("storage") on
top of /dev/md0 and /dev/md1. Finally, I allocated two logical
volumes on top of that: "one" is -L300GB and "two" is -L100GB.
mke2fs -j -m0 on /dev/storage/one and /dev/storage/two, and it would
seem everything was fine, but after copying data to the two volumes,
they would fail a fsck in pretty dramatic fashion (dozens of errors
indicating pretty severe filesystem corruption).
I'll skip all the steps I tried when reducing this down to a simple
reproducible test case, but the end result is this:
1) Take a 500GB disk (as before, it's SATA plugged into a card using
the sata_sil24 driver)
2) echo "0 482344960 linear 8:32 0" | dmsetup create one
echo "0 209715200 linear 8:32 482345000" | dmsetup create two
3) mke2fs -j -m0 /dev/mapper/one
mke2fs -j -m0 /dev/mapper/two
mount /dev/mapper/one /one
mount /dev/mapper/two /two
4) cd /one ; \
for i in `seq 0 3`; do dd if=/dev/zero bs=4K count=1M of=$i; done ; \
cd ; \
umount /one
cd /two ; \
for i in `seq 0 3`; do dd if=/dev/zero bs=4K count=1M of=$i; done ; \
cd ; \
umount /two
5) fsck -f /dev/mapper/one
fsck -f /dev/mapper/two
Both filesystems return many errors on fsck. This is very repeatable.
Note that this simplified reproduction case uses only the device
mapper: RAID is not involved, nor is LVM. "dmsetup table" says:
two: 0 209715200 linear 8:32 482345000
one: 0 482344960 linear 8:32 0
Just to be sure, I have run memtest86+ on the machine and badblocks on
the disk. Both came up clean. Partitioning the disk and mke2fs-ing
the partitions directly (i.e. no device-mapper), works fine. It's
only when using the device-mapper does the corruption happen. There
is nothing of interest logged in /var/log/messages or dmesg (I see the
usual messages around 'mount', but that's it).
Any suggestions? Many thanks,
David
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