After bringing it up, it showed some weird behavior. Sometimes it hung and the transmission application showed error message "Structure needs cleaning" for some torrents which were already in the download list.
Anyway I was able to log in to the linkstation and investigate the /var/log/message. It showed that the issue was with the XFS files system of the sda6 partition. You can find out the mount point of the sda6 using mount command or cat /proc/mounts command.
root@LS-VL406:~# cat /proc/mounts
rootfs / rootfs rw 0 0
/dev/root / ext3 rw,relatime,errors=continue,barrier=0,data=writeback 0 0
proc /proc proc rw,relatime 0 0
sysfs /sys sysfs rw,relatime 0 0
udev /dev tmpfs rw,nosuid,relatime,size=10240k,mode=755 0 0
devpts /dev/pts devpts rw,relatime,gid=4,mode=620 0 0
/dev/ram1 /mnt/ram tmpfs rw,relatime,size=15360k 0 0
/dev/sda1 /boot ext3 rw,relatime,errors=continue,barrier=1,data=writeback 0 0
/dev/disk1_6 /mnt/disk1 xfs rw,noatime,attr2,usrquota,grpquota 0 0
/dev/disk1_6 /opt xfs rw,noatime,attr2,usrquota,grpquota 0 0
root@LS-VL406:~# ls -la /dev/disk1_6
lrwxrwxrwx 1 root root 4 Mar 31 2015 /dev/disk1_6 -> sda6
Steps I followed to fix the issue,
1. Check whether the /mnt/disk1 is being used. kill or stop processes which are using the partition.
lsof | grep disk1
2. unmount the partition
umount /mnt/disk1
3. repair the partition
xfs_repair /dev/sda6
Then I rebooted the linkstation and it seems that the issue is resolved now.
Information which was available in the /var/log/messages file about the XFS corruption.
Mar 30 22:09:09 LS-VL406 kernel: Backtrace:
Mar 30 22:09:09 LS-VL406 kernel: [<c001b79c>] (dump_backtrace+0x0/0x114) from [<c001b8e4>] (dump_stack+0x18/0x1c)
Mar 30 22:09:09 LS-VL406 kernel: r6:c0481434 r5:c11dc800 r4:c01c870c
Mar 30 22:09:09 LS-VL406 kernel: [<c001b8cc>] (dump_stack+0x0/0x1c) from [<c018564c>] (xfs_error_report+0x54/0x64)
Mar 30 22:09:09 LS-VL406 kernel: [<c01855f8>] (xfs_error_report+0x0/0x64) from [<c01856b8>] (xfs_corruption_error+0x5c/0x78)
Mar 30 22:09:09 LS-VL406 kernel: [<c018565c>] (xfs_corruption_error+0x0/0x78) from [<c01aed28>] (xfs_bmap_read_extents+0x4f8/0x580)
Mar 30 22:09:09 LS-VL406 kernel: r6:00000000 r5:00000000 r4:c22bf000
Mar 30 22:09:09 LS-VL406 kernel: [<c01ae830>] (xfs_bmap_read_extents+0x0/0x580) from [<c01c870c>] (xfs_iread_extents+0x78/0xe0)
Mar 30 22:09:09 LS-VL406 kernel: [<c01c8694>] (xfs_iread_extents+0x0/0xe0) from [<c01a5dbc>] (xfs_bmapi_read+0xec/0x32c)
Mar 30 22:09:09 LS-VL406 kernel: r7:00000000 r6:c62b6240 r5:00000000 r4:c62b6270
Mar 30 22:09:09 LS-VL406 kernel: [<c01a5cd0>] (xfs_bmapi_read+0x0/0x32c) from [<c0181098>] (__xfs_get_blocks+0x180/0x524)
Mar 30 22:09:09 LS-VL406 kernel: [<c0180f18>] (__xfs_get_blocks+0x0/0x524) from [<c0181494>] (xfs_get_blocks+0x28/0x30)
Mar 30 22:09:09 LS-VL406 kernel: [<c018146c>] (xfs_get_blocks+0x0/0x30) from [<c0109658>] (__block_write_begin+0x1e4/0x4d4)
Mar 30 22:09:09 LS-VL406 kernel: [<c0109474>] (__block_write_begin+0x0/0x4d4) from [<c0109af8>] (block_write_begin+0x54/0x88)
Mar 30 22:09:09 LS-VL406 kernel: [<c0109aa4>] (block_write_begin+0x0/0x88) from [<c01816a0>] (xfs_vm_write_begin+0x48/0x7c)
Mar 30 22:09:09 LS-VL406 kernel: r6:18a07ebd r5:00000000 r4:18a07ebd
Mar 30 22:09:09 LS-VL406 kernel: [<c0181658>] (xfs_vm_write_begin+0x0/0x7c) from [<c00ac70c>] (generic_perform_write+0x198/0x20c)
Mar 30 22:09:09 LS-VL406 kernel: r8:cbd9e000 r7:00000000 r6:18a07ebd r5:00000143 r4:cbd9fd60
Mar 30 22:09:09 LS-VL406 kernel: [<c00ac574>] (generic_perform_write+0x0/0x20c) from [<c00ac7dc>] (generic_file_buffered_write+0x5c/0x90)
Mar 30 22:09:09 LS-VL406 kernel: [<c00ac780>] (generic_file_buffered_write+0x0/0x90) from [<c0186af0>] (xfs_file_buffered_aio_write+0xc0/0x150)
Mar 30 22:09:09 LS-VL406 kernel: r9:cbd9e000 r8:c62b6240 r6:c62b63f8 r5:00000000 r4:18a07ebd
Mar 30 22:09:09 LS-VL406 kernel: [<c0186a30>] (xfs_file_buffered_aio_write+0x0/0x150) from [<c0186f68>] (xfs_file_aio_write+0x174/0x1ec)
Mar 30 22:09:09 LS-VL406 kernel: [<c0186df4>] (xfs_file_aio_write+0x0/0x1ec) from [<c00e11a0>] (do_sync_write+0xa8/0xf0)
Mar 30 22:09:09 LS-VL406 kernel: [<c00e10f8>] (do_sync_write+0x0/0xf0) from [<c00e1a88>] (vfs_write+0xbc/0x150)
Mar 30 22:09:09 LS-VL406 kernel: r8:c000bca8 r7:cbd9ffa8 r6:007a81b0 r5:00010000 r4:c5c81f00
Mar 30 22:09:09 LS-VL406 kernel: [<c00e19cc>] (vfs_write+0x0/0x150) from [<c00e21dc>] (sys_pwrite64+0x80/0x94)
Mar 30 22:09:09 LS-VL406 kernel: r8:c000bca8 r7:000000b5 r6:c5c81f00 r5:00010000 r4:007a81b0
Mar 30 22:09:09 LS-VL406 kernel: [<c00e215c>] (sys_pwrite64+0x0/0x94) from [<c000bb00>] (ret_fast_syscall+0x0/0x2c)
Mar 30 22:09:09 LS-VL406 kernel: r6:00000000 r5:00000000 r4:18a07ebd
Mar 30 22:09:09 LS-VL406 kernel: XFS (sda6): Corruption detected. Unmount and run xfs_repair
