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  1. #1

    Need suggestions for a more powerful server

    I currently now have a Dual Opteron 250 with 2 GBs of RAM. The CPU is constantly overloaded, RAM is about 60-70% used and swap is about 50% used.

    I'm not sure where to go from here, and I know very little of actual server hardware Maybe I need to balance the load between 2 servers? Or should I go with trying to upgrade the current server to a more powerful machine? If so, I honestly don't know what could be upgraded.

  2. #2
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    sounds like your kernel has really crummy memory management or a bad io scheduler. Have you tried compiling a custom kernel?
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  3. #3
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    Well it does not have to be a errornous kernel. The above RAM usage is possible. Most kernels will try to move rarely used memory to the swap, so it can be used for disk cache and other applications.

    What kind of applications are your server running? If the server has to write often used memory to the swap, more RAM will probably increase your performance a lot, but if the swapped memory is never used more RAM probably wont help you much.

    If your applications is already optimized you could either go for a 4 CPU server or maybe move your SQL server (if you are using a SQL server) to another machine.

  4. #4
    [QUOTE=Edman]I currently now have a Dual Opteron 250 with 2 GBs of RAM. The CPU is constantly overloaded, RAM is about 60-70% used and swap is about 50% used.
    [QUOTE]

    Nice config.

  5. #5
    Obviously a Quad Opteron is going to be more powerful and run more efficiently. The folks here might have some ideas on how to reduce your load on the current config. If nothing works then you should be able to upgrade to a Quad Opteron for not too too much more. Wolle's idea about moving SQL to a seperate server is also worth investigating...it might be less expensive for you than the Quad.
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  6. #6
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    Quote Originally Posted by Edman
    I currently now have a Dual Opteron 250 with 2 GBs of RAM. The CPU is constantly overloaded, RAM is about 60-70% used and swap is about 50% used.

    I'm not sure where to go from here, and I know very little of actual server hardware Maybe I need to balance the load between 2 servers? Or should I go with trying to upgrade the current server to a more powerful machine? If so, I honestly don't know what could be upgraded.
    Do you know what is causing most of that load?
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  7. #7
    sounds like your kernel has really crummy memory management or a bad io scheduler. Have you tried compiling a custom kernel?
    Nope, I just went with what was currently on the server.

    The RAM usage for this is normal and increasing RAM to 4GBs is in fact my first thought here.

    Well it does not have to be a errornous kernel. The above RAM usage is possible. Most kernels will try to move rarely used memory to the swap, so it can be used for disk cache and other applications.

    What kind of applications are your server running? If the server has to write often used memory to the swap, more RAM will probably increase your performance a lot, but if the swapped memory is never used more RAM probably wont help you much.
    I am running a proxy site, so all server usage is done by a single script, CGIProxy. So effectively, it has a lot of computations to do, and then the webserver outputs the result. It never actually saves any data.

    Basically, I need to make this script run as fast as possible and not be so process intensive.

    Obviously a Quad Opteron is going to be more powerful and run more efficiently. The folks here might have some ideas on how to reduce your load on the current config. If nothing works then you should be able to upgrade to a Quad Opteron for not too too much more.
    This server is at HiVelocity, so if you could PM me a link to a pointer on how to upgrade to a Quad Opteron, I'd be quite willing to go with that because reducing load would work, but a more powerful server will be needed at one point in time.

  8. #8
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    How about your Apache configuration? Are you running your script under mod_perl? That can make a huge difference.
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  9. #9
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    Well a Dual Core Dual Opteron (265,270,275,280) would be a lot better performing than that box and probably a lot more affordable than a quad opteron.

    But I would try optmizing before continuing to that option. It could be pretty expensive compared to your current configuration.

  10. #10
    You may need to hire a consulting who will help you out or swith to a hosting compnay who will provide such service for free or as a paid service. From the description that you've maid - first concern - 50% of swap space used - You may have incorrect reading because of it is true then server of cource will be crawling. You have to run a combination of monitoring tools to find out what is the botleneck - in majority of cases when disk drive subsystem is not involved it is a RAM what cousng problems. Because of the specifics of your applucation you will have to have enough RAM to do not use swap at all - but this is just my guess - you have to have somebody looking into your server.
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  11. #11
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    Quote Originally Posted by Edman
    I currently now have a Dual Opteron 250 with 2 GBs of RAM. The CPU is constantly overloaded, RAM is about 60-70% used and swap is about 50% used.

    I'm not sure where to go from here, and I know very little of actual server hardware Maybe I need to balance the load between 2 servers? Or should I go with trying to upgrade the current server to a more powerful machine? If so, I honestly don't know what could be upgraded.
    What kernel are you running?
    What I/O scheduler are you using?
    What type of disks are in that server?
    What is your swapiness set to?

    Is there a noticeable performance impact on the sites hosted or are you just concerned by the numbers you are seeing?

  12. #12
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    Since there seem to be much confusion about the swapping, I will have to state (again) that the swapping does not have to be caused by a errornous kernel,

    If a server, like this one, mainly runs one process and probably have a lot of other unused processes, like mailservers and other unused processes running, then you actually want the kernel to swap their memory space to disk. By doing that the kernel gets more memory for disk caching and other purposes, which actually speeds up the server. So swapping in itself is not bad, only if often used processes are swapped then it becomes a bottleneck.

    Since the server seems to be running a proxy, then it is probably not a problem to do some kind of DNS round robin with another similiar server, which could be a whole lot cheaper than a quad server. I do not know much about CGIProxy, but if you are only using it as a proxy, you could try other proxies like squid or similiar which may perform better than CGIProxy.

  13. #13
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    Quote Originally Posted by wolle
    Since there seem to be much confusion about the swapping, I will have to state (again) that the swapping does not have to be caused by a errornous kernel,

    If a server, like this one, mainly runs one process and probably have a lot of other unused processes, like mailservers and other unused processes running, then you actually want the kernel to swap their memory space to disk. By doing that the kernel gets more memory for disk caching and other purposes, which actually speeds up the server. So swapping in itself is not bad, only if often used processes are swapped then it becomes a bottleneck.

    Since the server seems to be running a proxy, then it is probably not a problem to do some kind of DNS round robin with another similiar server, which could be a whole lot cheaper than a quad server. I do not know much about CGIProxy, but if you are only using it as a proxy, you could try other proxies like squid or similiar which may perform better than CGIProxy.

    It's a better idea to take a look at WHY it is swapping and determine if that is optimal or not. Yes, some things should swap. However, others should not and if the swapping is leading to degraded performance it should be addressed and not just overlooked as "it should swap"

  14. #14

    swapping

    Quote Originally Posted by wolle
    Since there seem to be much confusion about the swapping, I will have to state (again) that the swapping does not have to be caused by a errornous kernel,

    If a server, like this one, mainly runs one process and probably have a lot of other unused processes, like mailservers and other unused processes running, then you actually want the kernel to swap their memory space to disk. By doing that the kernel gets more memory for disk caching and other purposes, which actually speeds up the server. So swapping in itself is not bad, only if often used processes are swapped then it becomes a bottleneck.

    Since the server seems to be running a proxy, then it is probably not a problem to do some kind of DNS round robin with another similiar server, which could be a whole lot cheaper than a quad server. I do not know much about CGIProxy, but if you are only using it as a proxy, you could try other proxies like squid or similiar which may perform better than CGIProxy.

    This is absolutely true (about swap). Just 50% in my opinion is too much to swap. And I would still try to find bottleneck before adding another server. Round robin could be a problem for SSL sessions bu I don't know is this proxy been used for SSL anyway. My point is that adding gig or two RAM may solve the problem an it could be cheaper then adding another server, although I would agree that adding a second server could be cheaper that switching to quad server.
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  15. #15
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    Quote Originally Posted by tulix
    This is absolutely true (about swap). Just 50% in my opinion is too much to swap. And I would still try to find bottleneck before adding another server. Round robin could be a problem for SSL sessions bu I don't know is this proxy been used for SSL anyway. My point is that adding gig or two RAM may solve the problem an it could be cheaper then adding another server, although I would agree that adding a second server could be cheaper that switching to quad server.

    In the long term (2-3 months) upgrading to a quad versus a secondary server would be much cheaper.

    *making assumption*
    Given that it's an Opteron 248 the boad should support dual cores.

    Upgrading that server to a dual 265 or dual 270 would effectively make it a quad-core system at a cost savings versus a true quad.

    In this instance the tiny performance hit you would see from dual dual-core versus true quad cpu wouldn't even be noticeable as your application isn't dependent upon memory b/w

  16. #16
    Quote Originally Posted by Edman
    I currently now have a Dual Opteron 250 with 2 GBs of RAM. The CPU is constantly overloaded, RAM is about 60-70% used and swap is about 50% used.
    Edman,

    Could you post the output of

    $ uname -a
    $ uptime
    $ free

    These will show us your kernel version, load factor and Ram Usage.

    $ top

    can help identify which processes are using the most CPU and Memory.

    It could be any number of things that are slowing down your server. your webserver could be starting too many processes, or they could die and not free up resources.

    If 60-70% of the RAM is used, that should mean you have plenty. Linux likes to allocate lots of memory for buffers and caching disk files.

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