Обсуждение: AMD, Intel and RAID controllers

Hello all,

I'm looking for your general thoughts on CPU brand and HP disk controllers for a PostgreSQL server running Linux.  The
workloadis all over the place sometimes OLTP, sometimes huge/long report transactions, sometimes tons of inserts and
warehouseso I'm looking for overall good performance but not necessarily tuned to a specific task.  I'm basically
lookingat something in the ProLiant DL380 series which boils down to Intel Xeon 5500 or AMD Opteron 2600.  Are there
anynotable performance concerns regarding Postgres on either of these cpus? 

RAM will likely be in the 16GB range.  Any comments on bus speeds or other issues related to the RAM?

What is the opinion on HP disk controllers?  The standard controller on this server line is the Smart Array P400 (512MB
BBcache) although the option is available to go up to P600 or P800.  I plan to need about 500GB (8 146GB disks, raid
10). Are the HP controllers worth my time or should I be looking elsewhere? 

Finally, I'm thinking 10k RPM SAS drives are appropriate.  Does the substantial price increase for 15k RPM drives
reallyshow in the overall performance of the storage array? 

Thanks for your insights.


--
Benjamin Minshall <minshall@intellicon.biz>

On Thu, 1 Oct 2009, Benjamin Minshall wrote:

> I'm basically looking at something in the ProLiant DL380 series which
> boils down to Intel Xeon 5500 or AMD Opteron 2600.  Are there any
> notable performance concerns regarding Postgres on either of these cpus?

The Xeon 5500 series are very impressive performers.  The only reason I
could think of for why someone might want the older AMD design is if it
saved enouch money to buy more disks for an app limited by those.

> RAM will likely be in the 16GB range.  Any comments on bus speeds or other
> issues related to the RAM?

The Xeon 5500 models I've tested didn't seem to vary all that much based
on the memory speed itself.  It is important to pay attention to where the
major breaks in bus speed on the processor are though, because those bumps
really mean something.

> What is the opinion on HP disk controllers?  The standard controller on this
> server line is the Smart Array P400 (512MB BB cache) although the option is
> available to go up to P600 or P800.  I plan to need about 500GB (8 146GB
> disks, raid 10).  Are the HP controllers worth my time or should I be looking
> elsewhere?

Those are reasonable controllers, and the list archives here are filled
with a bias toward the P800.
http://www.nabble.com/Experience-with-HP-Smart-Array-P400-and-SATA-drives--td20788664.html
is a good sample, there are more.  The important thing to realize is that
RAID5 performance on the card is going to be awful no matter what you do,
since you're using RAID10 you should be fine.

> Finally, I'm thinking 10k RPM SAS drives are appropriate.  Does the
> substantial price increase for 15k RPM drives really show in the overall
> performance of the storage array?

If your app is limited by disk seeking and general latency, those can make
sense.  Ideally, you'd get enough RAM for caching that you're not hitting
the disks hard enough for the difference between them to matter so much.

--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD

On Fri, Oct 2, 2009 at 12:47 AM, alpesh gajbe <alpeshgajbe@gmail.com> wrote:

> We have a Proliant DL585 G5 with 16 cores and 32 GB Ram in the terms of
> processors we found that buying amd makes much more sense because in the
> same price we could put more processors
> on the machine and utilize the multiple cores effectively with PG

I just bought a machine with 12 2.2GHz AMD cores for less than it
would have cost me for 8 2.26GHz Nehelem cores, so yeah, I've found
the same thing.  And as you go up the price difference keeps getting
larger.

On Fri, 2 Oct 2009, Scott Marlowe wrote:

> On Fri, Oct 2, 2009 at 12:47 AM, alpesh gajbe <alpeshgajbe@gmail.com> wrote:
>
>> We have a Proliant DL585 G5 with 16 cores and 32 GB Ram in the terms of
>> processors we found that buying amd makes much more sense because in the
>> same price we could put more processors
>> on the machine and utilize the multiple cores effectively with PG
>
> I just bought a machine with 12 2.2GHz AMD cores for less than it
> would have cost me for 8 2.26GHz Nehelem cores, so yeah, I've found
> the same thing.  And as you go up the price difference keeps getting
> larger.

Huh, apparently I never sent this response...the whole Intel/AMD
comparison at this point really depends on how fast you need any
individual core to be.  The Intel i7 systems I was suggesting I like are
expensive, but they are the fastest cores around right now by a good
margin too.  If your demands are for lots of cores and you don't care how
much any one of them executes, then sure the AMD systems will save you
quite a bit of cash as suggested above.

But it's not difficult to run into situations with a PostgreSQL server
where you're bottlenecked waiting for something that can only run on one
core at a time.  Big reports and COPY are common examples.  If that's your
situation, there's no substitute for making the individual cores as fast
as feasible, and there the price premium Intel charges can easily be
worthwhile.

And as I already suggested a while ago, if you're disk bound, you
shouldn't be worrying about optimizing your processor choice very much at
all.  Get something cheaper and throw money at spindles and caching
instead.

--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD