On 18 Nov 2013, at 17:37, Alessandra Forti <[log in to unmask]> wrote:
> On 18/11/2013 17:14, Ewan MacMahon wrote:
>>> -----Original Message-----
>>> From: Testbed Support for GridPP member institutes [mailto:TB-
>>> [log in to unmask]] On Behalf Of Wahid Bhimji
>>>
>>> 1) Many sites have previously prefered to just have the loaded server
>>> nodes (prev R510s) with no expansion arrays. So perhaps there should be
>>> an option to have that configuration.
>>> (at Edinburgh we prefer the option with the arrays though)
>>>
>> We've preferred the servers at Oxford on the grounds that they cost
>> virtually the same (IIRC, at one point an R510 was actually marginally
>> cheaper from the portal than the equivalent disk array once you factored
>> in the RAID controller needed to use the array), and have all sorts of
>> minor advantages.
>>
>>> 3) 64G RAM is quite a lot - but maybe it doesn't really change the cost.
>>>
>> I'd say it's actually a little short for a box of this spec - our recent
>> machines have been 30TB usable with either 24 or 32GB of memory, so
>> roughly speaking, on the order of 1GB of RAM per 1TB of disk. Dave's
>> example spec would have 120TB of disk, so with 64GB of RAM it's about
>> half that ratio. On DPM disk servers, the RAM is basically all read cache,
>> so it's nice to have.
> Manchester is getting away with much less than this, but direct IO might change things. Wahid never sent his pros and cons.
>
Well when I was referring to pros and cons that was more about current atlas configuration issues.
Longer term I think theres only pros - the main one being it allows for much longer analysis jobs. Increased core counts is just going to mean more pressure on WN disk(s)….
But people are doing direct access now with their current hardware so I don't think it needs any radical changes.
On the RAM - its good point, Ewan that more the merrier really - maybe I should get some more for our current disk servers.
Wahid
> cheers
> alessandra
>>
>>> 4) Disk options: just looking at the dell normal prices - 3TB sata is
>>> listed at 386 while 4 TB NL sas is 605. which is quite a lot more. Anyway
>>> we maybe need to double check which offers the best value.
>>>
>> Indeed; our approach has been that this choice is up to the vendor to
>> decide which approach is the cheapest overall, but based on what we've
>> seen so far (that is, indicative hints, not formal tender responses) it
>> does seem that having more machines with 3TB disks works our slightly ahead
>> of a fewer boxes with 4TB disks option.
>>
>>> 6) Also warranty can be expensive and ought to be specified e.g. 4 yr pro
>>> support.
>>>
>> We've been buying five year warranties on everything for a while - it adds
>> trivially to the cost, and avoids the risk of having to write a machine off
>> prematurely for want of something trivial like a PSU. And given recent trends
>> in both our kit retirement schedule, and the (lack of) increase in disk
>> capacities, I would confidently expect storage servers to have a life of at
>> least five years, probably more like 7-8.
>>
>> All that said, my main feeling about this is that it would have been a good
>> idea if we'd done it earlier, but it's too late now given that most of us
>> have had the spend shifted from a planned FY14 to FY-blind-panic-do-it-now.
>>
>> Ewan
>
>
> --
> Facts aren't facts if they come from the wrong people. (Paul Krugman)
>
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