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  1. #1
    Join Date
    Mar 2007
    Posts
    71

    Deciding what type of VPS I require.

    Hello, I currently have a VPS hosted somewhere but I am looking into other options at this time. I am trying to figure out how much virtual and physical memory I will need as I expand.

    I am using the "top" command on my current host to get some numbers for my prediction. It is my understanding that the VIRT column in top is the total virtual memory being used by the sytem (RES + SWAP), where as RES would be the physical memory being used. If this is Correct, then I think this would be correct:

    Total RES = Physical RAM = Amount I need in Gauranteed RAM
    (Total VIRT - Total RES) = SWAP = Amount I need in burstable RAM

    Am I understanding this? I ask because based on my current top results, my physical (RES) memory looks how it should: 150MB used out of 256MB.
    However, it shows I am using about 1.3 GB of SWAP.

    I found this odd. So I talked to one of the support at my VPS host and he just kept saying that Virtuozzo's SLM method does not have a limit to SWAP or burstable limits.

    So is it possible that I am really using 1.3 GB SWAP and this is how much I'd need in burstable RAM?

    Is there a better command I can use to view how much burstable RAM I would need?

  2. #2
    Join Date
    Dec 2006
    Posts
    4,151
    Swap in Virtuozzo, to my knowledge, is shared by every VPS.

    In another words, it is not virtualized and the value shown should be the swap usage for the whole server.

    It's hard to predict burstable RAM, you have to calculate it yourself.

  3. #3
    Join Date
    Jan 2003
    Location
    SLC
    Posts
    2,278
    if running vituozzo in SLM mode

    type free -m at the command line and the numbler listed in the total mem will be your burstable ammount

  4. #4
    Join Date
    Mar 2007
    Posts
    71
    Quote Originally Posted by tsj5j
    Swap in Virtuozzo, to my knowledge, is shared by every VPS.

    In another words, it is not virtualized and the value shown should be the swap usage for the whole server.
    The 1.3GB I got was from manually calculating the numbers I got from the VIRT column of top. All of these numbers came from processes that I am running, so I doubt its for the whole server.

    Quote Originally Posted by HostingBig
    if running vituozzo in SLM mode

    type free -m at the command line and the numbler listed in the total mem will be your burstable ammount
    This is the same as my guaranteed RAM amount. 256MB.

  5. #5
    Join Date
    Jan 2003
    Location
    SLC
    Posts
    2,278
    then you have no burstabble RAM or your burst is 256 ???
    since i did not configure your server I do not know

  6. #6
    In UNIX terminology, virtual memory is not the same as SWAP. If we define virtual memory as memory without regards on how it is stored, a 1GB allocation if virtual memory could mean only 10MB is used in physical ram, 2MB used in SWAP and 988MB is unused.

    The VIRT column stands for how much virtual memory an app has allocated but this does not say anything about how much of it is actually used in physical memory or SWAP. So your 1.3GB you calculated is amount of virtual memory allocated, not SWAP. Applications tend to preallocate large amount of memory, but it doesn't get used unless the app uses it.

    Virtuozzo has no concept of SWAP (it uses 1 giant swap space for all users, but this is hidden from you), so when a provider tells you have 256MB guaranteed, then it is 256MB of virtual memory is guaranteed. So you are okay with your apps allocating 1.3GB of virtual memory, but the actual usage of that 1.3GB of virtual memory cannot exceed 256MB.

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