[Lustre-discuss] specifying OST

Wojciech Turek wjt27 at cam.ac.uk
Wed Jul 16 03:38:23 PDT 2008


Hi,

Type  'lfs help setstripe' on lustre client node

 >lfs help setstripe
setstripe: Create a new file with a specific striping pattern or
set the default striping pattern on an existing directory or
delete the default striping pattern from an existing directory
usage: setstripe <filename|dirname> <stripe_size> <stripe_index> 
<stripe_count>
       or
       setstripe <filename|dirname> [--size|-s stripe_size]
                                    [--index|-i stripe_index]
                                    [--count|-c stripe_count]
       or
       setstripe -d <dirname>   (to delete default striping)
        stripe_size:  Number of bytes on each OST (0 filesystem default)
                      Can be specified with k, m or g (in KB, MB and GB 
respectively)
        stripe_index: OST index of first stripe (-1 filesystem default)
        stripe_count: Number of OSTs to stripe over (0 default, -1 all)

Ok lets now using information above set that a particular file will be 
written to a particular OST.
For this exercise we assume we have a file system that consists of four OST
 
lctl dl
  0 UP mgc MGC10.143.245.201 at tcp a5f811be-0c46-09ee-2b5d-f59c569dba2e 5
  1 UP lov ddn_home-clilov-00000102280ca800 
d4470bbd-9917-1651-13d0-7736bfcac109 4
  2 UP mdc ddn_home-MDT0000-mdc-00000102280ca800 
d4470bbd-9917-1651-13d0-7736bfcac109 5
  3 UP osc ddn_home-OST0000-osc-00000102280ca800 
d4470bbd-9917-1651-13d0-7736bfcac109 5
  4 UP osc ddn_home-OST0001-osc-00000102280ca800 
d4470bbd-9917-1651-13d0-7736bfcac109 5
  5 UP osc ddn_home-OST0002-osc-00000102280ca800 
d4470bbd-9917-1651-13d0-7736bfcac109 5
  6 UP osc ddn_home-OST0003-osc-00000102280ca800 
d4470bbd-9917-1651-13d0-7736bfcac109 5

Lets say we would like to create file my_work.dat on ddn_home-OST0002
The command line for that will look like this:
 > lfs setstripe -i 3 -c 1 /home/my_home/my_work.dat

Now if you create file my_work.dat in /home/my_home it will be created 
on ddn_home-OST0002.

If you would like to make sure that new file is on the OST of you choice 
use 'lfs getstripe' command  to checkout striping pattern on the file 
you've just created.
 > lfs getstripe /home/my_home/my_work.dat

I know that manual doesn't give you an exact example how to do that but 
it gives an idea how striping works so please experiment with it to fond 
out what else you could do with lfs setstripe.

I hope it helps.

Cheers

Wojciech


Mag Gam wrote:
> BTW,
>
> I have read that manual page several times,
> http://manual.lustre.org/manual/LustreManual16_HTML/StripingAndIOOptions.html#50544707_pgfId-5529
>
> And I could still not find out how to do this...
>
>
> TIA
>
>
> On Tue, Jul 15, 2008 at 8:38 PM, Mag Gam <magawake at gmail.com> wrote:
>   
>> Really? How ?
>>
>> I been trying to figure this out.
>>
>> Can you please give me an example?
>>
>> TIA
>>
>> On Mon, Jul 14, 2008 at 7:16 AM, Dhruv <DhruvDesaai at gmail.com> wrote:
>>     
>>> You can use the lfs utility to route your file to any particular OST/
>>> s.
>>>
>>> On Jul 11, 4:38 pm, "Mag Gam" <magaw... at gmail.com> wrote:
>>>       
>>>> is it possible to create a file on a particular OST?
>>>>
>>>> TIA
>>>> _______________________________________________
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