fdatasync failed, I/O error

Our customer is running Postgresql v. 7.3.4 on Linux(Redhat 3.0 Ent.)
The application crashed and I am trying to understand what could have caused
this kind of problems:

fdatasync of log file 0, segment 2 failed: input/output error
PGSTAT: Error closing temp stats file
.../.../postgresql/global/pgstat.tmp.10278: Input/output error

I suppose they could be using NFS (I know, I know... we have to deal with
that. But could it be something else? A bad disk?)

Thank you,
Mike

======================================================================

From the database log:
-------------------------
... ... ... ...
2005-06-01 11:55:25 PANIC: fdatasync of log file 0, segment 2 failed:
input/output error
2005-06-01 11:55:25 LOG: server process (pid 16178) was terminated by
signal 6
2005-06-01 11:55:25 WARNING: Message from PostgreSQL backend:
The Postmaster has informed me that some other backend
died abnormally and possibly corrupted shared memory.
I have rolled back the current transaction and am
going to terminate your database system connection and exit.
Please reconnect to the database system and repeat your query.
2005-06-01 11:55:25 WARNING: Message from PostgreSQL backend:
The Postmaster has informed me that some other backend
died abnormally and possibly corrupted shared memory.
I have rolled back the current transaction and am
going to terminate your database system connection and exit.
Please reconnect to the database system and repeat your query.
2005-06-01 11:55:25 WARNING: Message from PostgreSQL backend:
The Postmaster has informed me that some other backend
died abnormally and possibly corrupted shared memory.
I have rolled back the current transaction and am
going to terminate your database system connection and exit.
Please reconnect to the database system and repeat your query.
2005-06-01 11:55:25 WARNING: Message from PostgreSQL backend:
The Postmaster has informed me that some other backend
died abnormally and possibly corrupted shared memory.
I have rolled back the current transaction and am
going to terminate your database system connection and exit.
Please reconnect to the database system and repeat your query.
2005-06-01 11:55:25 WARNING: Message from PostgreSQL backend:
The Postmaster has informed me that some other backend
died abnormally and possibly corrupted shared memory.
I have rolled back the current transaction and am
going to terminate your database system connection and exit.
Please reconnect to the database system and repeat your query.
2005-06-01 11:55:28 LOG: all server processes terminated; reinitializing
shared memory and semaphores
2005-06-01 11:55:28 LOG: database system was interrupted at 2005-06-01
02:05:21 IDT
2005-06-01 11:55:28 LOG: checkpoint record is at 0/268BF24
2005-06-01 11:55:28 LOG: redo record is at 0/268BF24; undo record is at
0/0; shutdown FALSE
2005-06-01 11:55:28 LOG: next transaction id: 23827; next oid: 25973
2005-06-01 11:55:28 LOG: database system was not properly shut down;
automatic recovery in progress
2005-06-01 11:55:28 LOG: redo starts at 0/268BF64
2005-06-01 11:55:28 LOG: ReadRecord: record with zero length at 0/269A9EC
2005-06-01 11:55:28 LOG: redo done at 0/269A9AC
2005-06-01 11:55:31 PANIC: fdatasync of log file 0, segment 2 failed:
Input/output error
2005-06-01 11:55:31 LOG: startup process (pid 16180) was terminated by
signal 6
2005-06-01 11:55:32 LOG: PGSTAT: Error closing temp stats file
/apps/sync/syncdata/sync/10000/server_metadata/postgr
esql/global/pgstat.tmp.10278: Input/output error
2005-06-01 12:47:28 LOG: database system shutdown was interrupted at
2005-06-01 11:55:28 IDT
2005-06-01 12:47:28 LOG: checkpoint record is at 0/268BF24
2005-06-01 12:47:28 LOG: redo record is at 0/268BF24; undo record is at
0/0; shutdown FALSE
2005-06-01 12:47:28 LOG: next transaction id: 23827; next oid: 25973
2005-06-01 12:47:28 LOG: database system was not properly shut down;
automatic recovery in progress
2005-06-01 12:47:28 LOG: redo starts at 0/268BF64
2005-06-01 12:47:28 LOG: ReadRecord: record with zero length at 0/269AA2C
2005-06-01 12:47:28 LOG: redo done at 0/269A9EC
2005-06-01 12:47:30 LOG: database system is ready