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Some questions about RAID

Discussion in 'Storage Drives' started by Artheas, 15 May 2006.

  1. Artheas

    Wise Guy

    Joined: 15 Mar 2006

    Posts: 2,124

    I'm trying to use two RAID 1 arrays on my machine, one for windows, and one for data storage.

    I've created the two arrays and set up windows on one of them, which is working fine.
    The other array consist of my old data storage drive with about 200Gb of data, an a newly formatted disk.
    Now when i go into windows, i cannot see the 2nd array.
    Is this because the two drives do not match data wise? It's the only thing i can thing of as ive tried everything else.
    If this IS the reason why they are not showing/working, then how is it that one recovers the array if one disk dies? If a blank replacement is put in its place, the system will see two different disks and nothing will happen.

    I was expecting the system to copy the data over to the new disk, but i guess theres no way for the system to know which is the master copy, even though one is blank.
     
  2. Poolybit

    Wise Guy

    Joined: 14 May 2006

    Posts: 1,174

    You probably have to rebuild the array in the RAID config manager. I've had that happen before, should be after the bios kinda time if its inbuilt.
     
  3. ChrisLX200

    Wise Guy

    Joined: 23 Jun 2004

    Posts: 2,141

    Location: Macclesfield

    I'm a bit confused here, but with your second array (the one that you 'can't see') - can you see either of the 2 disks in the array? In RAID 1 the system will only see one of the disks, the controler BIOS will have total control over the other (mirror) disk. Neither was there any need to format it - the controler again takes care of that.

    If you put a 'blank' disk in, and you can see BOTH disks from within Windows then they are not correctly setup as an array. The second one should be invisible. When disk writes are made to a RAID 1 array the controler writes the data to both disks, and every now and again it will run a check to ensure the data on both drives are identical - and if not data will be copied from one to the other.
     
  4. Artheas

    Wise Guy

    Joined: 15 Mar 2006

    Posts: 2,124

    I cannot see either of the two disks, windows doesnt seem to know that either one exists. But they are set up and are showing on NVRaid along with the windows array.
    They do show as separate disks when i disable RAID on the data storage drives, as expected.

    I cant see where the problem is then.. i may have to transfer all the data onto a spare HDD, and start the data storage array with 2 blank HDDs, but damn, tranferring the data takes ages, envermind back AND forth :'(
    (that's if that'll work lol)
     
  5. Artheas

    Wise Guy

    Joined: 15 Mar 2006

    Posts: 2,124

    Well it still made no difference.

    The array had to be initialised via windows too apparantly using disk manager, so i've done that and it seeems fine now.

    It took under 40mins to move the files to the IDE drive, but now it taking about 60 mins to move them back to the RAID array. Shouldnt moving the data to the array be faster, since write operations limit the speed of data transfer and the IDE is slower?
    I assumed that because the RAID array is 2 separate disks, write speed should only be just higher than that of a single disk.
     
  6. Soul Rider

    Gangster

    Joined: 29 Nov 2005

    Posts: 433

    Location: Milton Keynes

    No it won't RAID 1 is a mirror, meaning you have 2 disks and the data is written simultaneously to each disk so you have Main and you have a back-up duplicate copy. Writing will be done at the same speed, sometimes slower as it checks what is written, as a single drive.

    RAID0 and RAID5 give write performance increases.
     
  7. Artheas

    Wise Guy

    Joined: 15 Mar 2006

    Posts: 2,124

    I meant higher when compared to the IDE disk, as the disks in the array are SATA HDDs.

    I've just ran tests from HDTach on the arrays, and they are shockingly slow.
    The 80Gb RAID 1 array (windows) has a burst speed of 23.2MB/s, while the 250Gb RAID 1 array (data storage) has a burst speed of 50-60MB/s.

    Surely both of these should be at least 100+MB/s?

    On their own, the speeds were 150+MB/s.
     
    Last edited: 16 May 2006
  8. ChrisLX200

    Wise Guy

    Joined: 23 Jun 2004

    Posts: 2,141

    Location: Macclesfield

    Not that much difference between SATA1 and ATA. The burst speed is a poor indicator anyway, you need to look at sustained transfer, but RAID 1 (as already stated) is not going to be any better than a single disk and maybe slightly worse.