Re: deciding between amd and intel processor
От | Imre Oolberg |
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Тема | Re: deciding between amd and intel processor |
Дата | |
Msg-id | 4F6C6C68.8040007@auul.pri.ee обсуждение исходный текст |
Ответ на | Re: deciding between amd and intel processor (Scott Marlowe <scott.marlowe@gmail.com>) |
Список | pgsql-admin |
Hi! Lots of thanks for your attention and comments! This time we went with Dell AMD, with matching memory and processor speed of 1600 MHz, 6 x 600 gb 10k harddisks we intend to use in three mirrors striped together. We didnt yet dare to include SSD in pure form or with H700 CacheCade. (Although i read Gregg Smith's thougths about some ssd models which should be in itself suitable for db.) Imre On 03/21/12 03:37, Scott Marlowe wrote: > On Tue, Mar 20, 2012 at 5:42 PM, Imre Oolberg<imre@auul.pri.ee> wrote: >> Hi! >> >> My comerade has to decide for his so to say generic and a bit unpredicted >> PostgreSQL needs for web applications between Intel and AMD based server. >> For now it has been coming down to these processor choices >> >> 1. Dell PowerEdge R810 which has 2 x Intel® Xeon® E7-4830 2.13GHz, 24M >> cache 6.4 GT/s QPI, Turbo, HT, 8C, 1066MHz Max Mem processors > > Is this CPU really limited to 1066MHz memory? That's positively > ancient by today's standards. > >> as i see this makes total of 2 x 16 cores (or 2 x 16 threads) amd in total >> of 2 x 24 MB L2 cache > > HT cores aren't 100% as fast as a real core. They can get close > depending on the application. Generally the more CPU intensive the > better they do. The more you treat your CPUs like a data pump the > less it matters. It terms of performance, it's like something between > 16 and 32 cores. I'd guestimate it at about 24 or so. > >> 2. Dell PowerEdge R815 4 x AMD Opteron 6272, 2.1GHz, 16C, Turbo >> CORE, 16M L2/16M L3, 1600Mhz Max Mem processors >> >> as i see this makes total of 4 x 16 cores and in total of 4 x 16 MB L2 cache > > Yep. FAR more important is how many different memory banks you're now > capable of throwing at the problem. Each socket allows for a new > memory controller on the machine, since the newer Intels and AMDs have > integrated memory controllers. This reduces contention between CPUs > for memory access, and increases overall throughput. Given the much > slower main memory speed listed for the Intels I'd expect the AMD > machine to stomp the Intel machine into the mud in terms of > throughput. If the Intels are REALLY 1600, then the AMDs would still > get the nod, but it would be closer. > > So far based on what you've posted, I'd pick the AMD, mainly because > it has more memory bandwidth. > >> Other computer components are quite similar >> >> - 128 GB 1333 dual ranked lv rdimm MHz memory for AMD > > Is the cost of 1600MHz memory that much more? If it's a few hundred > or something, get the 1600MHz memory. If it's a few thousand, then > yeah, it might be worth sticking to 1333MHz memory and buying more > hard drives etc. > >> - 128 GB 1066 dual ranked lv rdimm MHz memory for Intel >> - PERC H700 Integrated RAID Controller, 1GB NV Cache >> - 4 x 600GB 10K RPM SAS 6Gbps 2.5in Hotplug Hard Drive > > I'm not that familiar with the PERC H700. While older model PERCs > were at best of questionable performance, the newer ones apparently > get decent reviews. that's a pretty small drive set for a machine > this massive. > >> Based on dell.com AMD variant comes about $14 k and Intel $17 k. > > Wow, that's a lot. A similar machine with 5 drive bays, 5 300G SAS > drives and an Areca 1880 SAS controller, and 4x16 AMD 6272 is right at > $10k from aberdeeninc.com, and that's with a 5 year warranty. For > that extra $4k you could probably upgrade to something with 16 or more > drives. IO is king of db performance. All the CPU in the world won't > help if you're waiting on your drive subsystem. > >> And i got following questions in mind >> >> 1. do you suggest this Intel or this AMD configuration taking also into >> account price? while it seems obvious to go with AMD so to say price-wise >> are there some hidden rocks behind the surface going with AMD (like L2 cache >> usage, overall system stability)? > > I'd recommend neither, as I'd rather chew off my own arm than ever > have to deal with Dell again. Way too many deals gone sour, and > horribly unknowledgable sales staff for me to deal with anymore. If I > have a purchasing officer somewhere in a big company to deal with them > they're OK. > > The L2 cache is no biggie. both the AMD and Intel CPUs listed are > pretty good performers. The equivalent intel chips cost WAY more than > the AMD ones tho, and honestly unless you're going for the top of the > line fastest 10 core CPUs the Intels aren't gonna be much faster, if > any. > >> 2. if it makes much sence to ask like this what could be considered on >> normal postgresql workload (with web applications) reasonable balance >> between cpu cores and memory system has? > > Without seeing some analysis of the current system, it's hard to say > what you need to upgrade really. What do tools like iostat, vmstat, > sar, iotop, iftop and so on say about the current system under load? > >> 3. it is intended to use debian on this system, now squeeze and some day >> wheezy, both hardwares most probably match quite well with debian and >> postgresql? > > You want a pretty late model kernel for a 64 core machine. Anything > released in the last two years will likely be ok, so yeah, Debian > Squeeze or Ubuntu 10.04 should be ok. > >> 4. it is intended not to use virtualization (KVM or Xen) but if needed, then >> just use different pg clusters as in pg_lsclusters, and controlling >> resources for each with shared_buffers etc, or should virtualization rather >> be considered? > > Only use virtualization if you really have to. Most of the time > you're better off with one cluster, or maybe two or three at most if > the usage patterns are really different. Virtulization has both > performance implications as well as data security implications, due to > questions about proper buffer flushing. > >> 5. i know that with four physical disks databases are generally recommended >> to use raid10 , but what would be recommended raid setup with six drives? > > RAID-10 on all 6 or RAID-1E on 5 with a hot spare is how I'd go. But > honestly, even 6 spinning disks seems like a low count. Now 6 SSDs is > another matter. How big is his data set? if it's pretty large then > he needs spinners, and in that case, throwing more at the problem is a > good idea. A 2U case that can hold 8 3.5" drives can hold a TON of > data, 8x3TB drives, even in RAID-10 gives you 12TBs. > > But all of this advice is kind of like the proverbial blind guy > describing an elephant. I'm not sure what the real workload looks > like. Yeah it's a web app, but that's kinda generic too. Banking, > content management, poker? Your friend needs to profile his current > system to see what's his choke points before he shells out $10k or > more for a db server. Be sad if all he needs is a RAID controller and > a box of 16 hard drives to make his current system performant and he > spent all that money on CPUs and memory he doesn't need, etc. >
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