Re: Ideal hardware spec?

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

On 08/26/2012 06:15 AM, Wido den Hollander wrote:
> CC'ing this one back to the list.
>
> On 08/25/2012 09:58 PM, Andrey Korolyov wrote:
>>>
>>> They should be much more reliable than regular USB sticks due to
>>> their SLC
>>> memory.
>>>
>>> You could also take a look at these:
>>> http://www.transcend-info.com/industry/products_details.asp?CatNo=2&SerNo=14&ModNo=28&Func1No=1
>>>
>>>
>>>
>>
>> Did you tried yet those or simular sticks for CEPH journal? Right now
>> I am using Intel 313`s, which is very fast and have durability/price
>> ratio a far higher than any imaginable MLC, but they occupying one HDD
>> slot which is a quite impractical.
>>
>
> No, I haven't tried, but I think it won't work.
>
> These kind of SLC chips don't do random writes that great, you'll
> probably get something like 4MB/sec in random writes.
>
> Bigger SSDs have more cells to spread the writes over, those small
> sticks don't.
>
> The Intel 3XX or 5XX serie should work just fine for journaling, I'd
> however recommend you change the Host Protected Area to ~50% of the
> available capacity to prevent write-degradation over time.
>
> Wido
> --
> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html

Not just write degradation, but undersubscribing the SSDs should 
hopefully help them last a little longer under such a heavy write 
workload.  We are doing 3 10GB journals per 180GB Intel 520 on our 
supermicro test node.

Mark