RAM Drives

Wednesday 20th April, 2005
Remember setting up DOS RAM drives back in the old days? Well, believe it or not, they're still around.

I have a new deployment of Domino servers here, each having 3GB RAM and 4 hyper-threaded Xeon processors which supply 8 logical CPU's. Using the notes.ini setting UPDATERS=8 I can now rebuild 8 indexes concurrently but, obviously, the disk i/o is immense. Rebuilding the indexes on a quieter drive will obviously help things somewhat, but where is best?

Domino is a 32-bit application and as such can only address 2GB of RAM. This means the remaining 1GB of ram is shared between the OS, anti-virus and erm...nothing. I really only need 2.5GB of RAM, but 3GB is a round number. So here I am thinking of RAM drives. I could create a nice 512MB partition in physical RAM just for temp files. It's going to fly.

I'm sure somebody has done this before, so what results did you get? Can anybody recommend any good, stable RAMdrive software for Win2K3?

  1. 1) Tony Kelleran Said: (20/04/2005 15:20:39 GMT) Gravatar Image
    RAM Drives

    At my last job we were close to getting a loaner solid state drive. My plan was to run Domino entirely on the drive. This would have been a fun project. At that time, SSD drives were - probably still are - expensive. Even with the loaner they wanted a deposit of a couple grand, I was only going to get a 6 GB SSD. I still would enjoy playing with it. Last weekend I had plans to install Domino on my USB thumb drive, but ran out of time. That would be a fairly easy thing to try as well. Never used any RAMDrive software on W2K3.

  2. 2) Ben Rose Said: (20/04/2005 15:23:34 GMT) Gravatar Image
    RAM Drives

    Tony,

    I just found a good use for my Mini iPod { Link }

  3. 3) Richard Schwartz Said: (20/04/2005 15:59:56 GMT) Gravatar Image
    RAM Drives

    It is not entirely true that Domino can only address 2 GB of RAM. It's a little more complicated than that. Each task -- and a Domino server consists of many tasks -- is capable of addressing 2 GB of virtual memory. The total of all the virtual address spaces for the Domino tasks can theoretically exceed the physical RAM. The reason Domino doesn't generally eat up all the RAM on machines with lots of physical RAM has more to do with the OS's limits on shared memory rather than the size of each task's virtual address space.

    Domino uses a significant amount of shared memory. Large blocks of the machine's physical memory are mapped to all the Domino tasks' virtual address space. Last I heard, Windows has a 1 GB limit on the total amount of user-mode shared memory. I'm not sure if this is a system-wide limit, or just for each set of tasks sharing memory. (In other words, I'm not sure if partitioned servers -- which don't share memory with each other -- can access a total of more than 1 GB of shared memory.)

    None of this, of course, invalidates the idea that you have spare RAM so a RAM drive for TEMP might help. I've thought of trying it on several occasions, but never actually done it.

    -rich

  4. 4) Mike McMahon Said: (28/04/2005 23:49:47 GMT) Gravatar Image
    RAM Drives

    A 32 bit operating system can address 4Gb of memory*

    Windows allows processes to allocate up to 2Gb of memory, reserving the upper 2Gb for itself (on a 4Gb machine.) Domino tends to chew through most of that.

    *Absent magic jiggery pokery.

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