Posted by: Anil | April 11, 2008

burstable… like a bubble?

What do service providers mean that X and Y are burstable, e.g. 256mb RAM burstable to 1GB? You aren’t really getting 1GB of RAM if you need it. That’s nonsense. What it means is you get 256mb RAM, with 768mb of SWAP! Swap is slow, disk based virtual memory. Its preferred to use memory as much as possible for your applications. To the Operating system the whole SWAP and RAM will look like logical contiguous memory.

At Entic.net our v.Dedicated Servers also have SWAP allocated. We give you double the RAM for SWAP (however, for the Basic package, it is 384MB SWAP).

Where we are different is that our SWAP is from 15K RPM SAS drives! Our servers don’t use the slower SATA drives, usually running around 5K RPM (for SWAP). So you could almost say our memory access is three times as fast.

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Responses

  1. No, it doesn’t mean that.

    Burstable means you have a guaranteed minimum of a resource, but if the host has spare capacity you can use that too (if there’s no contention).

    man FSS on a Solaris box sometime.

  2. Well, I was talking about Memory not CPU. FSS is for CPU.

    In Solaris zones, the memory is shared and is not dedicated to a zone (unlike LDoms) – so you can’t guarantee minimum dedicated RAM for a zone but only set a cap on it. (if we do a pmap, you’ll see some of those libraries could be mmap’ed to some other processes).

    Thats why I was speculating that when some of them say burstable thats what they are talking about.

    In addition, I was really trying to just say that you don’t really get 1GB RAM if you need it, only that it can get up to 1GB through VM (which could likely be SWAP, unless you have ton of GB’s of free memory left on server).

    That’s just my impression, please do correct me!

  3. Ah, you’re quite right, sorry. s
    Didn’t read that properly at all 🙂


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