[OT] Re: xfs_fsr on Buffalo Linkstation

[Jody Bruchon]

xfs_fsr defragments files in a "dumb" manner. An allocation is attempted for 
the size of the file and if the extent count of the new allocation is less than 
the old allocation, the file is copied to the new allocation and the original 
one is removed.

This is done with zero regard for any other filesystem circumstances. 
Defragmenting XFS can move your files to other allocation groups and generally 
scatter them about randomly. Any work done by XFS to try to keep files together 
when written initially can be blown away. Distance between files being accessed 
is a rarely discussed problem since defragmentation is commonly known about due 
to the influence of Windows, yet it has effects that can be worse than 
accepting a certain amount of file fragmentation.

There is no reason to run xfs_fsr for the entire system unless you let your 
disks fill up and then deleted a large amount of data. If you are worried about 
large files being fragmented, write a shell script using the find command to 
locate huge files and pass them along for individual defragmentation, but other 
than that you're almost certainly doing more harm than good.

Also, if you have 12TB worth of storage in that machine and you're using any 
kind of RAID then unless you have 10GbE you're not going to be able to slow the 
disks down enough in most use cases to NOT be able to totally saturate a 
gigabit link, so it's even more of a moot point. If your files are small and 
numerous enough and your accesses random enough to make the network outrun the 
disks, you won't benefit from the defrag work anyway because xfs_fsr has a good 
probability make them even slower than access relative to each other. All this 
effort to speed up the system could be making it even slower, plus your storage 
will be quite slow if xfs_fsr is running while you're trying to use the device 
for its intended purpose.

Read the XFS FAQ to get more information on this topic. The XFS people have 
covered all of these questions very comprehensively.

Jody Bruchon

On October 12, 2015 11:21:39 AM EST, Mike Dean  wrote:
>Sorry, but he gave you terrible advice.  I have to wonder if he's ever
>used
>XFS.
>
>The xfs_fsr utility will exit once it has finished defragging the
>filesystem.  What you really should do is this:
>
>1. Run xfs_fsr -v  manually, and let it run until it finishes.  Run it
>one
>more time, unless you still notice plenty of   extents: before: xx
>after:
>xx   messages.  Once you stop seeing these, move on to the next step.
>2. Set a cronjob to run DAILY to defrag the filesystem.  Not much
>fragmentation should be added daily, so this step should complete very
>quickly.
>
>If you wait a full month between defrags, it will take significantly
>longer
>to defrag and your overall performance will potentially suffer.  Keep
>in
>mind that you need to ensure there's always enough free space on your
>drive
>to make a duplicate of the largest file you keep on there.  Also, rules
>of
>thumb:
>
>If the drive is > 95%, it will fragment quickly.
>If the drive is < 90% full, it shouldn't fragment very much.
>
>So, try to keep it below 90% full; preferably, below 85% full.
>
>
>
>
>On Sun, Oct 11, 2015 at 6:23 PM, Matthias Andersson <
>matthias.anders...@pp1.inet.fi> wrote:
>
>> Hello,
>>
>> Very well, I might schedule the job once a month.
>>
>> //Matthias
>>
>>
>> On 11.10.2015 22.23, Hin-Tak Leung wrote:
>>
>>> I am curious about your plan of running it on a weekly basis.
>>>
>>> For a lightly used system, that seems a bit too frequent; for a
>system
>>> that's constantly being used, that may be justifiable, but
>>> then running it that frequently will probably (1) affect the
>performance
>>> of the system for regular tasks (during that hour your system's,
>>>   responsiveness will probably be bad, and that's a couple of hours
>>> per week, not a small proportion of time), (2) increase
>tear-and-wear.
>>>
>>> In any case, I'd probably only do a defrag every few months,
>>> or keep occupancy below a certain level (say, 60-70%) to keep
>>> fragmentation low though... just my 2 cents.
>>>
>>> 
>>> On Sun, 11/10/15, Matthias Andersson
>
>>> wrote:
>>>
>>>   Hello,
>>>
>>>   I own a Buffalo Linkstation Pro Quad 12 Tb which runs the
>>>   busybox OS.
>>>
>>>   The NAS uses the XFS filesystem and provides the xfs_fsr
>>>   defragmentation
>>>   tool. The problem I've noticed is that the program doesn't
>>>   obey the -t
>>>   (seconds) parameter, I've tried xfs_fsr -t 3600 /dev/md2 and
>>>   it runs
>>>   over an hour. I then tried with 8 hours but it didn't stop
>>>   there either.
>>>   The -p 1 flag seems to work...
>>>
>>>   I'm trying to set up a cron-job to run xfs_fsr for a couple
>>>   of hours on
>>>   a weekly basis.
>>>
>>>   //Matthias Andersson
>>>
>>>
>>>
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>> 

Re: xfs_fsr on Buffalo Linkstation

[Mike Dean]

Sorry, but he gave you terrible advice.  I have to wonder if he's ever used
XFS.

The xfs_fsr utility will exit once it has finished defragging the
filesystem.  What you really should do is this:

1. Run xfs_fsr -v  manually, and let it run until it finishes.  Run it one
more time, unless you still notice plenty of   extents: before: xx after:
xx   messages.  Once you stop seeing these, move on to the next step.
2. Set a cronjob to run DAILY to defrag the filesystem.  Not much
fragmentation should be added daily, so this step should complete very
quickly.

If you wait a full month between defrags, it will take significantly longer
to defrag and your overall performance will potentially suffer.  Keep in
mind that you need to ensure there's always enough free space on your drive
to make a duplicate of the largest file you keep on there.  Also, rules of
thumb:

If the drive is > 95%, it will fragment quickly.
If the drive is < 90% full, it shouldn't fragment very much.

So, try to keep it below 90% full; preferably, below 85% full.




On Sun, Oct 11, 2015 at 6:23 PM, Matthias Andersson <
matthias.anders...@pp1.inet.fi> wrote:

> Hello,
>
> Very well, I might schedule the job once a month.
>
> //Matthias
>
>
> On 11.10.2015 22.23, Hin-Tak Leung wrote:
>
>> I am curious about your plan of running it on a weekly basis.
>>
>> For a lightly used system, that seems a bit too frequent; for a system
>> that's constantly being used, that may be justifiable, but
>> then running it that frequently will probably (1) affect the performance
>> of the system for regular tasks (during that hour your system's,
>>   responsiveness will probably be bad, and that's a couple of hours
>> per week, not a small proportion of time), (2) increase tear-and-wear.
>>
>> In any case, I'd probably only do a defrag every few months,
>> or keep occupancy below a certain level (say, 60-70%) to keep
>> fragmentation low though... just my 2 cents.
>>
>> 
>> On Sun, 11/10/15, Matthias Andersson 
>> wrote:
>>
>>   Hello,
>>
>>   I own a Buffalo Linkstation Pro Quad 12 Tb which runs the
>>   busybox OS.
>>
>>   The NAS uses the XFS filesystem and provides the xfs_fsr
>>   defragmentation
>>   tool. The problem I've noticed is that the program doesn't
>>   obey the -t
>>   (seconds) parameter, I've tried xfs_fsr -t 3600 /dev/md2 and
>>   it runs
>>   over an hour. I then tried with 8 hours but it didn't stop
>>   there either.
>>   The -p 1 flag seems to work...
>>
>>   I'm trying to set up a cron-job to run xfs_fsr for a couple
>>   of hours on
>>   a weekly basis.
>>
>>   //Matthias Andersson
>>
>>
>>
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xfs_fsr on Buffalo Linkstation

[Matthias Andersson]

Hello,

I own a Buffalo Linkstation Pro Quad 12 Tb which runs the busybox OS.

The NAS uses the XFS filesystem and provides the xfs_fsr defragmentation 
tool. The problem I've noticed is that the program doesn't obey the -t 
(seconds) parameter, I've tried xfs_fsr -t 3600 /dev/md2 and it runs 
over an hour. I then tried with 8 hours but it didn't stop there either. 
The -p 1 flag seems to work...


I'm trying to set up a cron-job to run xfs_fsr for a couple of hours on 
a weekly basis.


//Matthias Andersson
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Re: xfs_fsr on Buffalo Linkstation

[Hin-Tak Leung]

I am curious about your plan of running it on a weekly basis.

For a lightly used system, that seems a bit too frequent; for a system
that's constantly being used, that may be justifiable, but
then running it that frequently will probably (1) affect the performance
of the system for regular tasks (during that hour your system's,
 responsiveness will probably be bad, and that's a couple of hours
per week, not a small proportion of time), (2) increase tear-and-wear.

In any case, I'd probably only do a defrag every few months,
or keep occupancy below a certain level (say, 60-70%) to keep
fragmentation low though... just my 2 cents.


On Sun, 11/10/15, Matthias Andersson  wrote:
 
 Hello,
 
 I own a Buffalo Linkstation Pro Quad 12 Tb which runs the
 busybox OS.
 
 The NAS uses the XFS filesystem and provides the xfs_fsr
 defragmentation 
 tool. The problem I've noticed is that the program doesn't
 obey the -t 
 (seconds) parameter, I've tried xfs_fsr -t 3600 /dev/md2 and
 it runs 
 over an hour. I then tried with 8 hours but it didn't stop
 there either. 
 The -p 1 flag seems to work...
 
 I'm trying to set up a cron-job to run xfs_fsr for a couple
 of hours on 
 a weekly basis.
 
 //Matthias Andersson

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Re: xfs_fsr on Buffalo Linkstation

[Denys Vlasenko]

On Sun, Oct 11, 2015 at 6:34 PM, Matthias Andersson
 wrote:
> Hello,
>
> I own a Buffalo Linkstation Pro Quad 12 Tb which runs the busybox OS.

busybox is not an OS.

http://busybox.net/FAQ.html#whatis
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Re: xfs_fsr on Buffalo Linkstation

[Matthias Andersson]

Hello,

Very well, I might schedule the job once a month.

//Matthias

On 11.10.2015 22.23, Hin-Tak Leung wrote:

I am curious about your plan of running it on a weekly basis.

For a lightly used system, that seems a bit too frequent; for a system
that's constantly being used, that may be justifiable, but
then running it that frequently will probably (1) affect the performance
of the system for regular tasks (during that hour your system's,
  responsiveness will probably be bad, and that's a couple of hours
per week, not a small proportion of time), (2) increase tear-and-wear.

In any case, I'd probably only do a defrag every few months,
or keep occupancy below a certain level (say, 60-70%) to keep
fragmentation low though... just my 2 cents.


On Sun, 11/10/15, Matthias Andersson  wrote:

  Hello,

  I own a Buffalo Linkstation Pro Quad 12 Tb which runs the
  busybox OS.

  The NAS uses the XFS filesystem and provides the xfs_fsr
  defragmentation
  tool. The problem I've noticed is that the program doesn't
  obey the -t
  (seconds) parameter, I've tried xfs_fsr -t 3600 /dev/md2 and
  it runs
  over an hour. I then tried with 8 hours but it didn't stop
  there either.
  The -p 1 flag seems to work...

  I'm trying to set up a cron-job to run xfs_fsr for a couple
  of hours on
  a weekly basis.

  //Matthias Andersson




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