Re: Xfs Access to block zero exception and system crash

[Sagar Borikar <sagar_borikar@pmc-sierra.com>]

Hi Dave,

Sagar Borikar wrote:
> Dave Chinner wrote:
>> On Sat, Jun 28, 2008 at 09:47:44AM -0700, Sagar Borikar wrote:
>>   Device Boot Start End Blocks Id System
>>> /dev/scsibd1             126         286       20608   83  Linux
>>> /dev/scsibd2             287        1023       94336   83  Linux
>>> /dev/scsibd3            1149        1309       20608   83  Linux
>>> /dev/scsibd4            1310        2046       94336   83  Linux
>>>     
>>
>> I'd have to assume thats a flash based root drive, right?
>>
>>   
> That's right,
>>> Disk /dev/md0: 251.0 GB, 251000160256 bytes
>>> 2 heads, 4 sectors/track, 61279336 cylinders
>>> Units = cylinders of 8 * 512 = 4096 bytes
>>>
>>> Disk /dev/md0 doesn't contain a valid partition table
>>>
>>> Disk /dev/dm-0: 107.3 GB, 107374182400 bytes
>>> 255 heads, 63 sectors/track, 13054 cylinders
>>> Units = cylinders of 16065 * 512 = 8225280 bytes
>>>     
>>
>> Neither of these tell me what /dev/RAIDA/vol is....
>> It is the device node to which /mnt/RAIDA/vol is mapped to. Its a 
>> JBOD with 233 GB size.
>>  
>>> But still the issue is why doesn't it happen every time and less 
>>> stress?
>>>
>>> I am surprised to see to let this happen immediately when the
>>> subdirectories increase more than 30. Else it decays slowly.
>>>     
>>
>> So it happens when you get more than 30 entries in a directory
>> under a certain load? That might be an extent->btree format
>> conversion bug or vice versa. I'd suggest setting up a test based
>> around this to try to narrow down the problem.
>>
>> Cheers,
>>
>> Dave.
>>   
> Thanks for all your help. Shall keep you posted with the progress on 
> debugging.
>
> Regards
> Sagar
>
After running my test for 20 min, when I check the fragmentation status 
of file system, I observe that it
is severely fragmented.

[root@NAS001ee5ab9c85 ~]# xfs_db -c frag -r /dev/RAIDA/vol
actual 94343, ideal 107, fragmentation factor 99.89%

Do you think, this can cause the issue?

Thanks
Sagar