xfs_repair fails after trying to format log cycle?

[Andrew Ryder <tireman@xxxxxxx>]

Hello,

I have an mdadm array with a xfs v5 filesystem on it and its begun to 
give me issues when trying to mount it as well as complete xfs_repair. 
Not sure if anyone might be able to shed some light on what is going on 
or how to correct the issue?
When I try and mount the fs, it complains with:

[  388.479847] XFS (md2): Mounting V5 Filesystem
[  388.494686] XFS (md2): metadata I/O error: block 0x15d6d39c0 
("xlog_bread_noalign") error 5 numblks 8192
[  388.495013] XFS (md2): failed to find log head
[  388.495018] XFS (md2): log mount/recovery failed: error -5
[  388.495090] XFS (md2): log mount failed


This is where its not making any sense for me, If I try and run 
"xfs_repair /dev/md2" it fails with:
Phase 1 - find and verify superblock...
        - reporting progress in intervals of 15 minutes
Phase 2 - using internal log
        - zero log...
xfs_repair: read failed: Input/output error
failed to find log head
zero_log: cannot find log head/tail (xlog_find_tail=-5)

fatal error -- ERROR: The log head and/or tail cannot be discovered. 
Attempt to mount the
filesystem to replay the log or use the -L option to destroy the log and
attempt a repair.


But if I run "xfs_repair -L /dev/md2" which gives:

Phase 1 - find and verify superblock...
        - reporting progress in intervals of 15 minutes
Phase 2 - using internal log
        - zero log...
xfs_repair: read failed: Input/output error
failed to find log head
zero_log: cannot find log head/tail (xlog_find_tail=-5)
xfs_repair: libxfs_device_zero write failed: Input/output error

then try and re-run "xfs_repair /dev/md2" it starts traversing the 
filesystem all the way to "Phase 7" then errors with:
Phase 7 - verify and correct link counts...
        - 14:36:55: verify and correct link counts - 33 of 33 
allocation groups done
Maximum metadata LSN (64:2230592) is ahead of log (0:0).
Format log to cycle 67.
xfs_repair: libxfs_device_zero write failed: Input/output error


Yet at this point I can now mount the filesystem..


Checking the drives with smartctl shows no errors nor does 'dmesg' show 
any hardware i/o or controller related errors...
I've tried scrubbing the array and no bad sectors are found either..

I'm running kernel 3.19.8 with xfsprogs 4.5.

Thanks,
Andrew