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I've never done anything with RAID before until now. I have 2 disks that were previously set up on this computer and I need to reformat the drives. From what I know about the current configuration, one drive is marked as active and the other one is not. I think this is incorrect as both of them need to be marked active. Obviously something I did wrong when I set it up the first time around.

Also, what would you recommend as far as raid level? I have 2 disks so I don't think I have much of an option. Raid 1? Thanks

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RAID1 (mirroring) is about your only useful options with 2 disks. You could also do RAID0, but it's a bit of a misnomer: it just does data striping, there's no redundancy, and so it usually isn't what you want.

As far as the comments about being "active", I assume you're seeing that somewhere in your RAID controller management interface? If you can give us more details, we can probably provide more information on that front, since that's probably very specific to your particular RAID setup.

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Sure Graeme, thanks. All I can remember is that before I formatted the drives the first time around, on the boot screen before the OS kicks in, I remembered seeing both drives listed in text mode and my option to enter the RAID util by pressing ctl D. Both of those drives had an "*" that denoted that they were active. When I reformatted these drives, only one drive now has an asterisk. I want to fix that. – Jim Nov 6 '09 at 19:10
I'm thinking that I may have to reformat these drives again. – Jim Nov 6 '09 at 19:11
Oh! Does your host OS see both drives individually, rather than see the RAID as a single drive? You could be using an onboard "FakeRAID" controller, without the proper RAID drivers. Then when you formatted one drive, it broke the RAID. If this is the case, you'll definitely have to redo the RAID, and then reinstall the OS with the proper RAID drivers at install time. – Graeme Nov 6 '09 at 19:26
It is actually a "Promise" controller. For some reason sees both drives and actually brings me to another question... WHen I installed Windows XP, I was forced to choose one of the drives; I couldn't select the array as a whole. Again, I'm really new to RAID so maybe this is normal. – Jim Nov 6 '09 at 19:29
I should mention that I had already downloaded the proper drivers before installing windows. That part of the install went just fine. I'm just hung up on how to set up these drives. For RAID 1, should I stripe them both or what? – Jim Nov 6 '09 at 19:34

If redundancy is your goal, RAID 1 with 2 drives is the way to go. If you want potentially faster disk access speeds, RAID 0 might help, but if you lose a disk it's gone for good (1/2 your data).

From your comments it sounds like you're dealing with a hardware RAID controller (not software-based RAID), so you will probably see better gains in performance if you go with RAID 0.

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If a single disk fails in a RAID-0, you lose all of the data, except in the off-chance that you are using a filesystem that can handle having half of itself missing. – Zimmy-DUB-Zongy-Zong-DUBBY Nov 6 '09 at 19:40
Thanks Matt, to achieve RAID 0, should I stripe both drives or what? Is it normal to see two drives on the windows install screen instead of one? – Jim Nov 6 '09 at 19:41
Yes, RAID 0 would be striping both drives and I believe they will show up as a 1 drive to the OS since your hardware RAID controller hands them off as a single drive. – Matt Nov 9 '09 at 19:12

2 drives are pretty limiting when it comes to RAID. RAID is used because it allows users to combine multiple discs into seemingly one drive, and create backups in case of disc failure. RAID is judged based on how fail safe it is against data loss, how much data can be stored on the drives (data density), and the data transfer rate.

In your case, your only options are RAID 0 and RAID 1. RAID 0 offers double the storage capacity of RAID 1. On the other hand, if one of your disc's fail, only RAID 1 will offer your data a backup. Plus, since RAID 1 replicates your data to two discs, seek times for your data are significantly faster. After all, searches can be happening in two places at once.

For your browsing pleasure, here is some more info on RAID. And yes, both drives need to be active.

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