The reason for an entire core peer osd is that it's trying to avoid context switching your CPU to death. If you have a quad-core processor with HT, I wouldn't recommend more than 8 osds on the box. I probably would go with 7 myself to keep one core available for system operations. This recommendation has nothing to do with GHz. Higher GHz per core will likely improve your cluster latency. Of course if your use case says that you only need very minimal through-put... There is no need to hit or exceed the recommendation. The number of cores recommendation is not changing for bluestore. It might add a recommendation of how fast your processor should be... But making it based on how much GHz per TB is an invitation to context switch to death.
On Sat, Aug 12, 2017, 8:40 AM Stijn De Weirdt <stijn.deweirdt@xxxxxxxx> wrote:
hi all,
thanks for all the feedback. it's clear we should stick to the 1GB/TB
for the memory.
any (changes to) recommendation for the CPU? in particular, is it still
the rather vague "1 HT core per OSD" (or was it "1 1Ghz HT core per
OSD"? it would be nice if we had some numbers like required specint per
TB and/or per Gbs. also any indication how much more cpu EC uses (10%,
100%, ...)?
i'm aware that this also depeneds on the use case, but i'll take any
pointers i can get. we will probably end up overprovisioning, but it
would be nice if we can avoid a whole cpu (32GB dimms are cheap, so lots
of ram with single socket is really possible these days).
stijn
On 08/10/2017 05:30 PM, Gregory Farnum wrote:
> This has been discussed a lot in the performance meetings so I've added
> Mark to discuss. My naive recollection is that the per-terabyte
> recommendation will be more realistic than it was in the past (an
> effective increase in memory needs), but also that it will be under much
> better control than previously.
>
> On Thu, Aug 10, 2017 at 1:35 AM Stijn De Weirdt <stijn.deweirdt@xxxxxxxx>
> wrote:
>
>> hi all,
>>
>> we are planning to purchse new OSD hardware, and we are wondering if for
>> upcoming luminous with bluestore OSDs, anything wrt the hardware
>> recommendations from
>> http://docs.ceph.com/docs/master/start/hardware-recommendations/
>> will be different, esp the memory/cpu part. i understand from colleagues
>> that the async messenger makes a big difference in memory usage (maybe
>> also cpu load?); but we are also interested in the "1GB of RAM per TB"
>> recommendation/requirement.
>>
>> many thanks,
>>
>> stijn
>> _______________________________________________
>> ceph-users mailing list
>> ceph-users@xxxxxxxxxxxxxx
>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>>
>
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