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  1. #1
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    Maximum amount of RAM on a server?

    It's been years since I've built a server, frankly there are too many choices (SDRAM vs. whatever) and configurations (SIMM vs. whatever) and manufacturers for me to figure out the answer.

    I need to know the pragmatic limit to RAM on an ordinary (non-blade) dual-Opteron server. I don't know how many memory slots are available, or what the largest chips are, etc. but I imagine we run out of physical space for memory well shy of the 64-bit architecture's addressing capability.
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  2. #2
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    I think on most Dual Opteron motherboards, the max RAM is 8GB.

    Edit: Forgot to mention, that there's also usually 4 DIMM slots. And lastly, I'm pretty sure the max DDR speed Opteron mobos can support is 400mhz.

  3. #3
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  4. #4
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    Now we're talking...

  5. #5
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    I thought you were just talking standard motherboards, but oh well.

    I think the biggest one stick of RAM you can buy is 4GB.

  6. #6
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    Originally posted by HstCreations
    I thought you were just talking standard motherboards, but oh well.
    I don't really know what a standard MB is. I have a Shuttle MB on my desktop, and an IBM Thinkpad. I have no clue about the MBs in my servers -- one shared account, one VPS and one dedicated.

    I hope we're talking 24MB on a board which fits in 1 or 2U of rackspace. Without 64-bit code, the only real feature of 64-bit architecture I can take advantage of today is the extra memory addressing capability.

    With this in mind, the app I'm developing is a memory HOG, in exchange for speed and efficient processor utilization. This morning, it occurred to me that it wouldn't make sense economically on my current dual-Xeon dedicated server because of the 4GB memory limit.

    Given a dual Opteron box, I'll be bumping into that 24GB limit sooner than I'll be running short of horsepower. I like the sound of 24GB in 1 or 2U better than I like the sound of three servers, or the cost of colocating a blade server.

  7. #7
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    If you're worried about economical sense, just wait till you see the prices for dual rank DDR or DDR2 in 1GB, 2GB, and larger DIMMS.

    If you could spread the load out among multiple servers with say 8GB, 12GB, or 16GB depending on the # of slots supported you'd be much better off and get a lot more bang for your buck.

  8. #8
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    You're right, I haven't looked at the prices for those bad boys. But why buy another server, if my current one is only utilizing half its processor cycles and can handle more RAM? I'm more interested in bang for the box.

    Yes, I'll probably be adding more servers before I'm maxing out the RAM on the first, but I won't be filling my memory slots with 512MB DIMMs either.

  9. #9
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    Even if you're not maxing out your CPU, my point would be it's cheaper to scale out your servers vs. scaling up the memory.

    As an example, retail web pricing on installed RAM before any specials or discounts at Dell:

    A 2850, or 1850 Dell PowerEdge Server both with 6 DIMM slots. Note this is for the memory in the system only, not the server.

    6GB Total, 6x1GB Single Ranked = $2,100
    8GB Total, 4x2GB Dual Ranked = $3,800
    12GB Total 4x2GB Single, 2 Double Ranked = $13,050
    12GB Total, 6x2GB Single Ranked = $15,000

    A four proc server like the 6850 with 16 DIMM Slots... again, memory pricing only...

    Prices for single ranked in 16GB or total generally run less than the 6 DIMM slot 2850, 1650 due to the availability of 16 DIMM slots on the 6850 that can use 1GB single ranked. However you also take on additional chassis costs of $2k+ per server, 208v power requirements, and additional 2-3U of rack space.

    32GB Total, 16x2GB Dual Ranked = $17,000


    My only point would be to look at the total cost as once you run out of slots for your DIMMS and need 2GB Dual Ranked Ram the cost just doesn't scale in your favor.

    Better off buying an additional server and maxing it out with more 1GB Single Ranked if that'll work with your project. Might have some added benefits such as allowing you to cluster or load balance.
    Last edited by sshepherd; 07-21-2005 at 06:16 PM.

  10. #10
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    Taken under advisement.

    Originally posted by sshepherd
    However you also take on additional chassis costs of $2k+ per server, 208v power requirements, and additional 2-3U of rack space.
    Don't forget the costs of securing and managing an additional server.

  11. #11
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    With more than one machine you also dont have a single point of failure. (Unless of course losing 1 server makes the others useless even if they are still running)

  12. #12
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    I intend to scale up to two clusters, in two datacenters, with UltraDNS handling failover and loadbalancing. I'll set up a spreadsheet and run the numbers someday soon, before committing to a hardware plan. Two clusters of two servers each, with room to expand the memory as needed, is what I'm thinking. Once those are set up with a minimum amount of RAM/maximum open slots, I can keep adding memory for a while before I need to add more servers.

  13. #13
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    Here's a related thread, where better than the lounge to talk about motherboards?

    http://www.webhostingtalk.com/showth...hreadid=429389

  14. #14
    I've seen up to 16GB.. my Opteron box has 8GBs installed.

    http://defense.unitedfrag.com/stats

    The box is just for web-hosting, no other services run on it.

  15. #15
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  16. #16
    yesir it is, much cheaper solution for web-hosting over dedicated

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