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Re: Speed of rm compared to reiserfs (slow) - and switching logdevices

To: Eric Sandeen <sandeen@xxxxxxxxxxx>
Subject: Re: Speed of rm compared to reiserfs (slow) - and switching logdevices
From: Török Edwin <edwintorok@xxxxxxxxx>
Date: Sun, 28 Sep 2008 22:27:07 +0300
Cc: xfs@xxxxxxxxxxx
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On 2008-09-28 21:25, Eric Sandeen wrote:
> Török Edwin wrote:
>   
>> On 2008-09-26 10:41, Török Edwin wrote:
>>     
>>> On 2008-09-26 02:54, Dave Chinner wrote:
>>>   
>>>       
>>>> On Thu, Sep 25, 2008 at 11:16:35AM +0300, Török Edwin wrote:
>>>>   
>>>>     
>>>>         
>>>>> On 2008-09-25 03:27, Dave Chinner wrote:
>>>>>     
>>>>>       
>>>>>           
>>>>>> On Wed, Sep 24, 2008 at 11:43:13AM +0300, Török Edwin wrote:
>>>>>>       
>>>>>>         
>>>>>>             
>>>>> Thanks for the suggestions, the time for rm has improved a bit, but is
>>>>> still slower than reiserfs:
>>>>>
>>>>> time rm -rf gcc
>>>>>
>>>>> real    1m18.818s
>>>>> user    0m0.156s
>>>>> sys     0m11.777s
>>>>>
>>>>> Is there anything else I can try to make it faster?
>>>>>     
>>>>>       
>>>>>           
>>>> Buy more disks. ;)
>>>>
>>>> XFS is not really optimised for single disk, metadata intensive,
>>>> small file workloads.
>>>>     
>>>>         
>>> I have 6 disks, in raid10 :)
>>>   
>>>       
>> I moved the logdevice to another disk (not part of RAID array), and now
>> the speed of rm is down to 30 seconds!
>>
>> I didn't find any documentation on how to convert an XFS fs with
>> internal log device to use external, so I did the following:
>> # xfs_db -x /dev/mapper/vg--all-lv--opt
>> xfs_db>sb
>> xfs_db> write logstart 0
>> xfs_db> quit
>>
>> The zero the logdevice, and mount using logdev=. This worked.
>>
>> However if I now use xfs_repair on this filesystem it restores the
>> internal log. Is there a way to make this change permanent? (i.e. switch
>> permanently to using external log?)
>>     
>
> Odds are you need to also set the logstart in the other superblocks:
>
> xfs_db> sb 0
> xfs_db> write logstart 0
> xfs_db> sb 1
> xfs_db> write logstart 0
>
> ...
>
> you could script this with xfs_db -c
>   

Thank you, xfs_repair now no longer changes the logdevice.

Best regards,
--Edwin

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