[Lustre-discuss] specifying OST

Thu Jul 17 03:58:51 PDT 2008

Yes. This is what I was thinking too. I suppose I can use rsync to
move the data from old to backup directory. But what if users starts
to write to to the OST that is going to be decommissioned. Is there a
way to make it readonly?

On Thu, Jul 17, 2008 at 6:19 AM, Wojciech Turek <wjt27 at cam.ac.uk> wrote:
> Hi,
>
> I guess
>
> First set the striping pattern on the root directory of the file system to
> not stripe to OST that you are planning to decommission. Then Scans each
> file and directory for it's striping pattern using 'lfs getstripe' command
> then if the file is striped to the OST you want to decommission simply copy
> the file to backup directory. Make sure that backup directory has set a
> striping pattern to not to stripe to the OST you are moving data away from.
> Then you simply replace the old files with files from backup directory.
> After you finish deactivate the OST. Information on how to deactivate an OST
> you can find in the manual.
>
> I hope it helps.
>
> Wojciech
>
>
> On 16 Jul 2008, at 12:08, Mag Gam wrote:
>
>> Thank you. This makes very good sense. (you should wiki this :-)
>>
>>
>> A similar question, is it possible to move from a striped volume to a
>> non-striped volumes because I want to decommission an OST. For
>> instance,
>>
>> 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
>>
>>
>> I want to decommission 5 (ddn_home-OST0002-osc-00000102280ca800), and
>> I have a striped and non-striped data. The goal is I don't want to
>> disturb the clients. I have the option to disable writes but not
>> reads.
>>
>> Any ideas how I can do that?
>>
>>
>> TIA
>>
>>
>> On Wed, Jul 16, 2008 at 6:38 AM, Wojciech Turek <wjt27 at cam.ac.uk> wrote:
>>>
>>> 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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