[ceph-users] Bareos and libradosstriper works only for 4M sripe_unit size

Gregory Farnum gfarnum at redhat.com
Mon Oct 16 16:42:35 PDT 2017


That looks right to me... PRs for the Ceph docs are welcome! :)

On Mon, Oct 16, 2017 at 4:35 PM Alexander Kushnirenko <kushnirenko at gmail.com>
wrote:

> Hi, Gregory, Ian!
>
> There is very little information on striper mode in Ceph documentation.
> Could this explanation help?
>
> The logic of striper mode is very much the same as in RAID-0.  There are 3
> parameters that drives it:
>
> stripe_unit - the stripe size  (default=4M)
> stripe_count - how many objects to write in parallel (default=1)
> object_size  - when to stop increasing object size and create new objects.
>  (default =4M)
>
> For example if you write 132M of data (132 consecutive pieces of data 1M
> each) in striped mode with the following parameters:
> stripe_unit = 8M
> stripe_count = 4
> object_size = 24M
> Then 8 objects will be created - 4 objects with 24M size and 4 objects
> with 8M size.
>
> Obj1=24M    Obj2=24M    Obj3=24M    Obj4=24M
> 00 .. 07         08 .. 0f         10 .. 17         18 .. 1f  <--
> consecutive 1M pieces of data
> 20 .. 27         21 .. 2f         30 .. 37         38 .. 3f
> 40 .. 47         48 .. 4f         50 .. 57         58 .. 5f
>
> Obj5= 8M    Obj6= 8M    Obj7= 8M    Obj8= 8M
> 60 .. 67        68 .. 6f        70 .. 77        78 .. 7f
>
> Alexander.
>
>
>
>
> On Wed, Oct 11, 2017 at 3:19 PM, Alexander Kushnirenko <
> kushnirenko at gmail.com> wrote:
>
>> Oh!  I put a wrong link, sorry  The picture which explains stripe_unit
>> and stripe count is here:
>>
>>
>> https://indico.cern.ch/event/330212/contributions/1718786/attachments/642384/883834/CephPluginForXroot.pdf
>>
>> I tried to attach it in the mail, but it was blocked.
>>
>>
>> On Wed, Oct 11, 2017 at 3:16 PM, Alexander Kushnirenko <
>> kushnirenko at gmail.com> wrote:
>>
>>> Hi, Ian!
>>>
>>> Thank you for your reference!
>>>
>>> Could you comment on the following rule:
>>> object_size = stripe_unit * stripe_count
>>> Or it is not necessarily so?
>>>
>>> I refer to page 8 in this report:
>>>
>>>
>>> https://indico.cern.ch/event/531810/contributions/2298934/attachments/1358128/2053937/Ceph-Experience-at-RAL-final.pdf
>>>
>>>
>>> Alexander.
>>>
>>> On Wed, Oct 11, 2017 at 1:11 PM, <ian.johnson at stfc.ac.uk> wrote:
>>>
>>>> Hi Gregory
>>>>
>>>> You’re right, when setting the object layout in libradosstriper, one
>>>> should set all three parameters (the number of stripes, the size of the
>>>> stripe unit, and the size of the striped object). The Ceph plugin for
>>>> GridFTP has an example of this at
>>>> https://github.com/stfc/gridFTPCephPlugin/blob/master/ceph_posix.cpp#L371
>>>>
>>>>
>>>>
>>>> At RAL, we use the following values:
>>>>
>>>>
>>>>
>>>> $STRIPER_NUM_STRIPES 1
>>>>
>>>> $STRIPER_STRIPE_UNIT 8388608
>>>>
>>>> $STRIPER_OBJECT_SIZE 67108864
>>>>
>>>>
>>>>
>>>> Regards,
>>>>
>>>>
>>>>
>>>> Ian Johnson MBCS
>>>>
>>>> Data Services Group
>>>>
>>>> Scientific Computing Department
>>>>
>>>> Rutherford Appleton Laboratory
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> ceph-users mailing list
>>>> ceph-users at lists.ceph.com
>>>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>>>>
>>>>
>>>
>>
>
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