• Disk Mirroring

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    WSAndyAinscow
    AskWoody Lounger
    January 11, 2003 at 8:10 pm #381692

    Could someone please tell me if the following is possible and if it is possible then recommend a product.

    Server with Win2000 (plus exchange 2000 server, IIS) and 2 identical sized SCSI Harddisks (not RAID system).
    Can one perform a mirror of one HD to the other whilst the server software is running, say in the middle of the night when no users are active? Would anit-virus software be likely to cause a problem?

    If the server has to be downed for the mirror does anyone have a product they recommend and it should preferable be usable via a script to automate the procedure (ie instructions – shutdown, put floppy in drive, restart, type go at prompt, go home, come back next day, remove floppy, reboot).

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    • WSAndyAinscow
      AskWoody Lounger
      January 11, 2003 at 8:12 pm #644528

      ps. If it can be done with a RAID system but not as detailed in main post then please tell me so.

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    • WSAndyAinscow
      AskWoody Lounger
      January 12, 2003 at 2:59 pm #644630

      I’ve sorted it out now – Win 2000 Server has it’s own mirroring software as long as the disks are set as dynamic.

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      • WSDrew
        AskWoody Lounger
        January 26, 2003 at 5:47 am #647947

        Sorry I didn’t see your post earlier. Just checking out the various sections on the lounge.

        Yes, Windows 2000 has the capability to create mirrors, raids, striped drives and spanned drives.

        This is all done by using dynamic disks. It’s very easy to setup a disk as ‘dynamic’, just right click on it within disk management, and you’ll have the option to upgrade to dynamic, or downgrade back to basic. A few ‘warnings’ about dynamic disks though. First of all, dynamic disks won’t pop from machine to machine very well. Some hard drives can ‘fail’ as dynamic disks, but work just fine as a basic disk. (We had problems with a lot of our IDE IBM 20 and 30 gig drives).

        Also, just FYI, Mirror’s are handy, but I recommend that your have your OS running on a set of mirrored drives, and your data running on a RAID. If you don’t have enough drives to do that (you need at least 5 (2 for the mirror, and 3 for the RAID). I don’t think you can setup a RAID on the OS (not using the OSes RAID capabilities) drive.

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        • WSAndyAinscow
          AskWoody Lounger
          January 27, 2003 at 9:41 am #648197

          Thanks, I have since found out about dynamic disks and inbuilt mirroring support in Win 2000 Server.

          It

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          • WSDrew
            AskWoody Lounger
            January 27, 2003 at 7:10 pm #648350

            Actually I think a mirror is a Raid 0 configuration. I think. I don’t think you can do a RAID on the OS drive (where you have 3 drive tolerance) anyways.

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            • WSAndyAinscow
              AskWoody Lounger
              January 28, 2003 at 6:13 am #648480

              It appears you can mirrot the OP system and without a RAID configuration.
              I tried putting 2 old IDE HD’s in my development machine and installed Win 2000 server, set dynamic and did a mirror. It didn’t object to anything. However I couldn’t test a failure so easily so I assume it is properly functional. Maybe this is actually a RAID in the strict definition of the terminology, but there was no separate RAID controller hardware.

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            • WSDrew
              AskWoody Lounger
              January 28, 2003 at 3:49 pm #648597

              Right, I wasn’t talking about a hardware RAID controller. With a dynamic disk you can mirror (which you can do to the OS drive), you can also span. With dynamic disks, you don’t have partitions, you have volumes. With partitions, you can only make 4, a primary and 3 extended. With volumes, you can make as many as you like. You can also ‘resize’ a volume, which you can’t do with a partition (well, I think Partition Magic lets you, but it’s not an OS function). A spanned drive is simple a volume that you can have overflow onto multiple drives. Then there is striped. A striped drive is sort of like a mirror, however, instead of duplicating the data on two drives, you split the data between the two drives. With a striped drive, if you have a 4 meg file, 2 megs will be on one drive, and 2 megs on the other. Thus when it is reading the file, you are reading it twice as fast. The last option is to setup a RAID. You can do this strictly with Windows 2000’s dynamic disks, no controller necessary. To make a RAID, you have to have 3 drives. It is like a striped drive set, but the third drive is a parity drive. So you get the speed of a stripe, but the redunancy of a mirror.

              What I was saying about a dynamic disk RAID, is that you can’t set it up on the OS drive. You can however set it up for your data drives. (In fact, you can have a mirrored set and RAID set on a total of 3 drives. Take two 30 gig drives, and a 20 gig drive. Put the OS on 10 gigs of one of the 30’s, then mirror it on the other 30. Then you can make a RAID with the remaining 20 gigs on both 30s along with the 20 gig drive. With a RAID you lose 1/3 (I think if you add more disks the ratio goes down…so you save more disk space), so with 3 20 gig sections, you get a 40 gig raid drive.

              They take a little while to initialize, but you can physically remove one of the drives, and everything will keep going.

              To get a RAID on the OS partition/volume, you would need a RAID controller.

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            • WSAndyAinscow
              AskWoody Lounger
              January 29, 2003 at 8:50 am #648829

              Thankss for the info. I’ll digest it and make certain I understand what you are saying.

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            • WSDrew
              AskWoody Lounger
              January 29, 2003 at 8:03 pm #648978

              Have fun. I spent some time on learning that stuff…but now I’m extremely happy I did….

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            • WSAndyAinscow
              AskWoody Lounger
              January 30, 2003 at 6:12 am #649115

              I’ll try to. My speciality is software, hardware is much more of a sideline and usually workstations not servers.

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