Re: [SLE] Raid 0 speed question

From: H du Plooy (linuser_at_ananzi.co.za)
Date: 10/04/03

  • Next message: Leen de Braal: "Re: [SLE] Computer resets spontaneously" 
    To: suse-linux-e@suse.com
Date: Sat, 04 Oct 2003 17:10:47 +0200

    On Sat, 2003-10-04 at 00:31, Carlos E. R. wrote:
    > The 03.09.29 at 20:15, H du Plooy wrote:
    >
    > > 2. Use kernel software raid to mirror the current Western Digital
    > > Caviar 5400rpm 2mb cache 10gb drive with a 10gb partition on a new (but
    > > now very cheap) 5400rpm 40gb drive. The remaining 30gb on the new disc
    > > would be /home
    > >
    > > Which setup would be faster?
    >
    > A mirror is not faster: write operations have to be done on both hard
    > disks. At best, it will be the same. Read opertions could be faster,
    > perhaps. A raid 5 setup (which is not a mirror) of three disks on three
    > separate cables (IDE) should be faster.
    >
    > Another solution: distribute your partitions. For example, you can have
    > /opt in one disk, and the rest on the other: X environment and
    > applications start faster. Swap partitions can also be distributed.

    I'm sorry, I confused two things when writing my question. I meant
    (hope I have the number right!) Raid-0 i.e. two partitions on two
    seperate discs as one of double the size - and hopefully double the
    speed. What I meant to write is that I would not need or want to mirror
    the disc, as most of the stuff on the disc is replaceable: music
    collection which I own all the CDs of, e-mail foder which I back up to
    CD once or twice a week, same for docs and pics, the rest is just the OS
    installation and settings which would take some time to set up again,
    but no big loss if something breaks.

    Thing is I'm not thinking of buying an PCI Raid controller - for the
    price difference I could just as well get a 7200rpm 8mb cache drive.
    What I would really like to know is how stiping (sp?) the 5400rpm discs
    with kernel based software raid would perform compared to a new 7200rpm
    disc. The ones I've built into new machines lately - mostly the
    standard Seagate 7200rpm 2mb cache models - are really much faster than
    the drive I have.

    Thanks for the suggestions. Distributing partitions over discs is
    another option, but finding a good solution will take time. Which
    filesystems will get used more? I assume with local mail delivery +
    spamassasin, /var would get used heavily, and I use a fair bit of swap.
    Put them on seperate discs, or both on the faster of the two drives? Or
    shall I use the slower disc for the filesystems that get read more often
    and the faster disc for the filesystems that get written to more often?
    I have a feeling the time I would spend figuring out the best partition
    sceme wouldn't be worth the money I save. It is definitely something
    that I'd like to get to know inside out, but I can't afford the time for
    that just now.

    Thanks for the ideas!

    Hans 

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