>> Would it be 4 objects of 24M and 4 objects of 250KB? Or will the last
4 objects be artificially padded (with 0's) to meet the stripe_unit?
It will be 4 object of 24M + 1M stored on the 5th object
If you write 104M : 4 object of 24M + 8M stored on the 5th object
If you write 105M : 4 object of 24M + 8M stored on the 5th object + 1M
on 6th object
Maged
On 2017-10-17 01:59, Christian Wuerdig wrote:
> Maybe an additional example where the numbers don't line up all so
> nicely would be good as well. For example it's not immediately obvious
> to me what would happen with the stripe settings given by your example
> but you write 97M of data
> Would it be 4 objects of 24M and 4 objects of 250KB? Or will the last
> 4 objects be artificially padded (with 0's) to meet the stripe_unit?
>
> On Tue, Oct 17, 2017 at 12:35 PM, Alexander Kushnirenko
> <kushnire...@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
> <kushnire...@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
> <kushnire...@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.john...@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
>
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