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/at > tachments/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/at >> tachments/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/gridFT >>> PCephPlugin/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@lists.ceph.com >>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >>> >>> >> >
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