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

To: Török Edwin <edwintorok@xxxxxxxxx>
Subject: Re: Speed of rm compared to reiserfs (slow) - and switching logdevices
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Sun, 28 Sep 2008 13:25:35 -0500
Cc: xfs@xxxxxxxxxxx
In-reply-to: <48DFB20D.2020609@xxxxxxxxx>
References: <48D9FDA1.8050701@xxxxxxxxx> <20080925002724.GA27997@disturbed> <48DB48E3.3020104@xxxxxxxxx> <20080925235453.GF27997@disturbed> <48DC9227.6060908@xxxxxxxxx> <48DFB20D.2020609@xxxxxxxxx>
User-agent: Thunderbird 2.0.0.17 (Macintosh/20080914)
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

-Eric


> Best regards,
> --Edwin
> 
> 

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