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  1. #1

    How to evenly split IO on 2 harddisks?

    I have a server with 2 harddisks, and it is used to host a site of mainly forums. I want to use both harddisks to minimize the IO load.

    My sites are quite SQL intensive, and logfile builds up quite fast too (700M/day). There are very few mails. Backup is not a problem, I can keep a mirror data of each disk on the other and sync them daily.

    I am thinking about:

    Disk 1: OS + sites + mail + temp
    Disk 2: MySQL + logs

    But I am not sure if that's the best config. Please give me some suggestions.

  2. #2
    Join Date
    Apr 2005
    Location
    Sweden
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    241
    How about creating a little two disk raid-0 array using the linux software raid tools, would that be an option? That would distribute the load pretty evenly over the 2 disks. If one disk dies, all the data is lost though so keep a backup too somewhere.

  3. #3
    Join Date
    Jun 2003
    Location
    Janesville, Wi
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    1,516
    RAID0 combines two drives into one. If one drive fails, the whole thing dies.

    This is what you want to do:

    Use RAID1 in which, for example, you have two 80 GB hard drives. You have 80 GB usable space, but the IO is balanced between the two.

    Use RAID5 in which, for example, you have three to five 80 GB hard drives. You have 160 GB usable space, but the IO is balanced over all drives on the array. If one drive fails, the array becomes RAID1.

    If you're going to use RAID, I highly recommend getting a 3Ware RAID Controller. RAID is the BEST solution for IO balancing. On my database server, processing 500 queries per second and a few gigs of logs per day, I am using RAID5 with 3 hard drives at 10000RPM each.

    Do NOT use RAID0 for IO balancing.

    For a great website on the differences between EVERY level of RAID possible, visit this link: http://www.acnc.com/04_01_00.html

    They explain and graphically show how RAID works at every level.
    Last edited by Jakiao; 04-24-2005 at 11:32 AM.
    Jakiao

  4. #4
    RAID-5 is high read, slow write. Not really a *great* option.

    And to actually answer the originals question, yes, I believe that would be the best setup for your situation.

    But a question...

    Why do you get such a huge logfile? What errors do you keep having?
    .

  5. #5
    Join Date
    Jun 2003
    Location
    Janesville, Wi
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    1,516
    http://www.acnc.com/04_01_05.html Check out their talks on RAID5.

    Personally, I have converted all major servers to RAID5. Previously, our database server was on a RAID1 array. The change to RAID5 has actually increased the speed at which the data has been served.
    Jakiao

  6. #6
    Do you run a forum, with a lot of posting?

    Besides, that wasn't his question. He already has a server, with 2 HDDs. He wanted to know the best setup for that, and explained to us his situation with his site.
    .

  7. #7
    Join Date
    Jun 2003
    Location
    Janesville, Wi
    Posts
    1,516
    Yes, and I replied with various RAID options that he should strongly consider. Are we agreeing with that by any chance?
    Jakiao

  8. #8
    Thank you all for your suggestions.
    Unfortunately, RAID is not an option for me.
    I just want to know, from your experience, what is the proportion of disk IO of database, home, tmp, swap, log, mail, OS... so that I can split the load evenly on 2 harddisks.

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