Corrupted database's files (linux RAID5 + PostgreSQL 8.3.0)

Hi,

Today one of the disk was marked as as failed .... and now some files
are corrupted.
I've decided to copy the pgsqldata directory and try to fix PG_VERSION
(see below for information - what PostgreSQL don't like) files ... and
see if the database will come up.
During copying files and etc. I'll be open for any other idea how to
deal with the problem ;)

PostgreSQL's log offer me to run initdb (HINT message from LOG file) -
what will happen if then I try to copy the rest ot the structure into
the newly created database cluster ?

linux (Slackware 12.0.0), software RAID5 (partition based) + PostgreSQL
8.3.0:

Here's what happen (from dmesg):

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# uname -a
Linux xeonito 2.6.21.5 #3 SMP Tue Oct 2 16:20:48 EEST 2007 i686 Intel(R)
Xeon(R) CPU E5335 @ 2.00GHz GenuineIntel GNU/Linux

---------------------------------------
# dmesg
sd 0:0:3:0: SCSI error: return code = 0x08000002
sdd: Current: sense key=0x4
ASC=0x44 ASCQ=0x0
Info fld=0x0
end_request: I/O error, dev sdd, sector 159620863
sd 0:0:3:0: SCSI error: return code = 0x08000002
sdd: Current: sense key=0x4
ASC=0x44 ASCQ=0x0
Info fld=0x0
end_request: I/O error, dev sdd, sector 159617119
raid5: Disk failure on sdd1, disabling device. Operation continuing on 4
devices
......

RAID5 conf printout:
--- rd:5 wd:4
disk 0, o:1, dev:sdb1
disk 1, o:1, dev:sdc1
disk 2, o:0, dev:sdd1
disk 3, o:1, dev:sde1
disk 4, o:1, dev:sdf1
RAID5 conf printout:
--- rd:5 wd:4
disk 0, o:1, dev:sdb1
disk 1, o:1, dev:sdc1
disk 3, o:1, dev:sde1
disk 4, o:1, dev:sdf1

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# cat /proc/mdstat
Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5]
[raid4] [multipath] [faulty]
md1 : active raid5 sdb1[0] sdf1[4] sde1[3] sdd1[5](F) sdc1[1]
585924608 blocks level 5, 8192k chunk, algorithm 2 [5/4] [UU_UU]

md0 : active raid5 sdb2[0] sdf2[4] sde2[3] sdd2[5](F) sdc2[1]
390053888 blocks level 5, 1024k chunk, algorithm 2 [5/4] [UU_UU]

unused devices: <none>

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And here's what the partitions look like:

# fdisk -l /dev/sdb

Disk /dev/sdb: 249.8 GB, 249865175040 bytes
255 heads, 63 sectors/track, 30377 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sdb1 1 18237 146488671 83 Linux
/dev/sdb2 18238 30377 97514550 83 Linux

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Kernel parameters:

echo 4200000000 > /proc/sys/kernel/shmmax
echo 4200000000 > /proc/sys/kernel/shmall
sysctl -w vm.overcommit_memory=2

echo 8192 > /sys/block/md0/md/stripe_cache_size
echo 8192 > /sys/block/md1/md/stripe_cache_size

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Both md0 and md1 are used from PostgreSQL - initially it was not design
to use the whole disk sdb-sdf, but due to size requirement I join also
the other unused space to be used by PostgreSQL.

And here's the Postgre's log (FATAL message is coming when I try to
connect to the database, of course this is the case for the most
interesting database ... some other small databases are working fine):

LOG: received smart shutdown request
LOG: autovacuum launcher shutting down
LOG: shutting down
LOG: database system is shut down
LOG: could not create IPv6 socket: Address family not supported by protocol
LOG: database system was shut down at 2008-05-20 17:54:17 EEST
LOG: autovacuum launcher started
LOG: database system is ready to accept connections
FATAL: "base/16399" is not a valid data directory
DETAIL: File "base/16399/PG_VERSION" does not contain valid data.
HINT: You might need to initdb.

Of course base/16399/PG_VERSION contains something strange not the
version information:

# cat base/16399/PG_VERSION
X

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