Swap Space - SGI

This is a discussion on Swap Space - SGI ; Can someone tell me how (or a link) to increase swap space on an SGI Octane. We upgraded the RAM to 1GB and I need to grow the swap space from 250Mb to 1.5Gb. I'm been thrown to the wolves ...

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  1. Swap Space

    Can someone tell me how (or a link) to increase swap space on an SGI
    Octane. We upgraded the RAM to 1GB and I need to grow the swap space
    from 250Mb to 1.5Gb. I'm been thrown to the wolves with these boxes.
    I've got about 15 production machines I need to do this with. I was
    really hoping to do this without a total reconfig.

    Thanks,
    Mike-b

  2. Re: Swap Space

    In article ,
    Mike-b wrote:
    :Can someone tell me how (or a link) to increase swap space on an SGI
    :Octane. We upgraded the RAM to 1GB and I need to grow the swap space
    :from 250Mb to 1.5Gb. I'm been thrown to the wolves with these boxes.
    :I've got about 15 production machines I need to do this with. I was
    :really hoping to do this without a total reconfig.

    There is more than one way to increase swap space. The traditional
    way is to increase the size of the swap partition, which is
    *usually* partition 1 on the root disk, with partition 0 being the
    kernel. Several years ago, SGI changed things around a little so
    that partition 1 is now by default *before* partition 0 on the
    root disk; if you have that setup, the implication is that you
    probably do not have any room for the swap partition to grow into.

    The second traditional way is to move the swap partition on to
    another disk. There are a couple of tricks at the prom level
    that you have to know when you are building this configuration
    in order to get IRIX to default to the new swap partition.

    The third way is to create an empty partition and use swap -a
    to activate the partition. If you use this option, then you
    should edit /etc/fstab to add a swap resource; see the -m option
    of the 'swap' command.

    The fourth and newest way is to create a large file (e.g., via
    the "mkfile" command) and use swap -a to add that file. If you
    use this option, then you should edit /etc/fstab to add a swap
    resource; see the -m option of the 'swap' command.


    The most efficient of these is a raw swap partition carefully
    positioned in the sweet spot of a drive that is used *only* for
    that swapping, with the drive being on a different controller than
    anything else (i.e., no I/O contention on the bus.) But if you
    are not going to go to that much trouble for efficiency, then
    the least efficient of the methods, swap to a file, is still
    pretty efficient; the relative slowdown is measurable, but
    relatively minor compared to the hit you take by using swap
    space in the first place.


    You should also consider whether what you really need is just
    *virtual swap*. If your programs are in the habit of reserving
    a lot of memory but then not actually using most of the memory,
    then you can usually get away with telling the system to
    overcommit on memory, knowing that most of the programs aren't
    going to need their larger memory at any particular time. This situation
    turns out to be fairly common: whenever a program fork()'s,
    the system reserves enough memory to completely duplicate the
    original process, but the fork()'d process often then exec()'s
    a smaller program. Virtual swap can be added using swap -v .
    The size of virtual swap at boot time can be controlled via
    /etc/config/vswap.options
    --
    This signature intentionally left... Oh, darn!

  3. Re: Swap Space

    Thanks to everyone for all of the great suggestions and "how-to's".

    Mike-b



    John Damm SÝrensen wrote in message news:<3F454012.708@nomail.hovedpuden.dk>...
    > Mike-b wrote:
    >
    > > Can someone tell me how (or a link) to increase swap space on an SGI
    > > Octane. We upgraded the RAM to 1GB and I need to grow the swap space
    > > from 250Mb to 1.5Gb. I'm been thrown to the wolves with these boxes.
    > > I've got about 15 production machines I need to do this with. I was
    > > really hoping to do this without a total reconfig.
    > >
    > > Thanks,
    > > Mike-b

    > On a modern unix(r) like operating system like IRIX the total memory
    > space available for processes is made up of physical memory plus the
    > allocated swap space.
    > So if you have just added more memory in order to prevent swapping you
    > will not need to add swap as well.
    >
    > If you have large processes that forks small programs like lp you will
    > probably be safe with virtual swap.
    >
    > Hopes this clarifies things.
    >
    > /John


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