Re: SSD journal suggestion

[Mark Nelson <mark.nelson@inktank.com>]

On 11/07/2012 10:12 AM, Atchley, Scott wrote:
> On Nov 7, 2012, at 10:01 AM, Mark Nelson <mark.nelson@inktank.com> wrote:
>
>> On 11/07/2012 06:28 AM, Gandalf Corvotempesta wrote:
>>> 2012/11/7 Sage Weil <sage@inktank.com>:
>>>> On Wed, 7 Nov 2012, Gandalf Corvotempesta wrote:
>>>>> I'm evaluating some SSD drives as journal.
>>>>> Samsung 840 Pro seems to be the fastest in sequential reads and write.
>>>
>>> The 840 Pro seems to reach 485MB/s in sequential write:
>>> http://www.storagereview.com/samsung_ssd_840_pro_review
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>>
>> I'm using Intel 510s in a test node and can do about 450MB/s per drive.
>
> Is that sequential read or write? Intel lists them at 210-315 MB/s for sequential write. The 520s are rated at 475-520 MB/s seq. write.

Doh, wrote that too early in the morning after staying all night 
watching the elections. :)  You are correct, it's the 520, not the 510.

>
>>   Right now I'm doing 3 journals per SSD, but topping out at about
>> 1.2-1.4GB/s from the client perspective for the node with 15+ drives and
>> 5 SSDs.  It's possible newer versions of the code and tuning may
>> increase that.
>
> What interconnect is this? 10G Ethernet is 1.25 GB/s line rate and I would expect your Sockets and Ceph overhead to eat into that. Or is it dual 10G Ethernet?
>
> Scott
>

This is 8 concurrent instances of rados bench running on localhost. 
Ceph is configured with 1x replication.  1.2-1.4GB/s is the aggregate 
throughput of all of the rados bench instances.

>> TV pointed me at the new Intel DC S3700 which looks like a very
>> interesting option (the 100GB model for $240).
>>
>> http://www.anandtech.com/show/6432/the-intel-ssd-dc-s3700-intels-3rd-generation-controller-analyzed
>>
>> Mark
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>