On 06/06/2014 11:27 AM, zou wonder wrote:
Hi Wido:
Thanks for your kindness, i checked the codes just now, seems there
were no overload related thing in CRUSH codes. It is a little bit not
consistent with the CRUSH paper.
So if the %100 utilized OSD is returned, the objects will still be
written on the underlined storage device?
Yes. If the OSD is up/in it will be selected by CRUSH and data will be
read from it and written to it.
Again, having one OSD being 100% utilized and the rest 40% is not
something you'll see very often since you stripe data over objects.
How about the device failure case? All the objects on the failure
device will be replicated to the good ones? once the device is
recoverd, the data will be replicated back?
When the OSD fails recovery will kick in after 5 minutes and the data
will find a new location.
If the OSD comes back, the data goes back to that OSD.
Best Regards
Zou
On Fri, Jun 6, 2014 at 4:27 PM, Wido den Hollander <wido@xxxxxxxx> wrote:
On 06/06/2014 10:14 AM, zou wonder wrote:
Hi buddies,
I am doing investigation on Ceph and Swift,and I am newbie to Ceph.
I am unclear to the behaviour of the Ceph when there is overload
situation.
According to the doc, when Ceph do CRUSH, if it find the OSD is overload,
it will skip it to select the other OSD. It means if the OSD don't get
overloaded
the object should be put in this OSD. So how about the original on put on
this OSD when it is not get overloaded?
Can we read it ? When doing CRUSH , the OSD will be skip.
CRUSH will not take any performance characteristics into account. If a OSD
is 100% utilized it will still be selected by CRUSH.
Keep in mind however that Block Devices are striped in 4MB chunks and the
same happens for Objects stored via the RADOS Gateway.
If my understanding is wrong, please correct me.
Best Regards,
zou
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Wido den Hollander
42on B.V.
Ceph trainer and consultant
Phone: +31 (0)20 700 9902
Skype: contact42on
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Wido den Hollander
42on B.V.
Ceph trainer and consultant
Phone: +31 (0)20 700 9902
Skype: contact42on
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