Raid1 mirror behavior normal?

[rsbennett00]

It's been a while since I dealt with two drives in raid1, it's almost always 0 for performance or 5/6 in large pools. So I've got this system that was setup in raid1 in case of drive failure so we could boot to the other drive and now one of them has failed but I can't get it to boot off the one left working. Selecting it in bios just gives a boot failure message. Here's the really weird part: When I boot into raid management, it shows the array degraded with one disk missing and if I try to remove the missing drive, it tells me to demote it instead, so I try to demote the missing drive and I get an "invalid request" error. If I try to delete the entire array, it tells me "deleting a raid set deletes all data on each disk". That can't be right, why would it wipe the disk completely? Shouldn't it just change the mbr or something?

 

[staticlag]

What drive controller are you using?

 

[gerbiaNem]

Don't delete the raid set whatever you do. See the degraded status is a great step. If you have another drive lying around to install a temp OS on, us that and convert the disk to a single to recover the data. I'm assuming that you're using an Intel controller.

 

[mwroobel]

You could also pull the good drive and move it to a new machine temporarily to get off any important data (in case anything goes wrong during the remirror.)

 

[rsbennett00]

It's a mac mini server, 10.7. I was being vague on purpose to try and keep the apple hate at bay. Sure, I can slave it to another machine and get the data off, but the data isn't a big deal. I was under the impression that when half of a 2disk mirror failed, the other half would keep going, it would boot, everything would operate, and the array would just be in a degraded state until another disk was added. So considering time machine is a far easier data retention solution, what's the point to raid1 if I have to rebuild the OS anyway?

 

[gerbiaNem]

I don't have much experience with Raid 1 on Apple hardware, but I did setup a Mac Mini server for my friend's office one time. Did you create the raid array in the OS or in the raid rom? Going the OS route might cause issues on an active boot drive.

The real concerning part is that you can't demote the remaining drive. Were you hit by a power surge by any chance?

 

[drescherjm]

I was under the impression that when half of a 2disk mirror failed, the other half would keep going, it would boot, everything would operate, and the array would just be in a degraded state until another disk was added. So considering time machine is a far easier data retention solution,

That is how raid is supposed to work. I know linux software raid works this way however fakeraid sometimes falls short.

 

[rsbennett00]

I don't have much experience with Raid 1 on Apple hardware, but I did setup a Mac Mini server for my friend's office one time. Did you create the raid array in the OS or in the raid rom? Going the OS route might cause issues on an active boot drive.

The real concerning part is that you can't demote the remaining drive. Were you hit by a power surge by any chance?

A surge would be extremely unlikely, this is at work so the whole building is on power isolated from the grid and this being in our server room, it has its own tripp-lite ups.

I created the array with disk utility off the lion flash drive before formatting and installing the OS (since osx would not allow me to mirror a drive with data already on it <eyeroll>). I'm unsure if there's an actual raid rom but being apple and being a mini, I doubt it but I'll look.

 

[mwroobel]

It's a mac mini server, 10.7. I was being vague on purpose to try and keep the apple hate at bay. Sure, I can slave it to another machine and get the data off, but the data isn't a big deal. I was under the impression that when half of a 2disk mirror failed, the other half would keep going, it would boot, everything would operate, and the array would just be in a degraded state until another disk was added. So considering time machine is a far easier data retention solution, what's the point to raid1 if I have to rebuild the OS anyway?

Ah, no reason to worry about Mac haters. To manually rebuild a RAID 1 array using Mac OS X Snow Leopard and Lion, administrators should perform these steps:

Ensure all disks are properly installed and connected.
Open the Mac OS X Disk Utility.
From the left-hand window console, highlight the degraded RAID 1 array. Degraded arrays should display using red text. Then, ensure the RAID tab is selected from within the right-hand window.
One of two resolutions will be available. If the array’s degradation is due to inconstant data, “Failed” will display next to the problematic disk. If the trouble is due to a bad or missing drive, “Offline” will appear next to the drive.
Clicking the Rebuild button will prompt Mac OS X to review disk inconsistencies and repair arrays degraded due to inconsistent data. If a drive no longer mounts and is missing, highlight the missing or failed drive and click the - icon, then drag the replacement drive from the left-hand pane to the right-hand window, and then click the Rebuild button to repair the array.

 

[rsbennett00]

Ah, no reason to worry about Mac haters. To manually rebuild a RAID 1 array using Mac OS X Snow Leopard and Lion, administrators should perform these steps:

Ensure all disks are properly installed and connected.
Open the Mac OS X Disk Utility.
From the left-hand window console, highlight the degraded RAID 1 array. Degraded arrays should display using red text. Then, ensure the RAID tab is selected from within the right-hand window.
One of two resolutions will be available. If the array’s degradation is due to inconstant data, “Failed” will display next to the problematic disk. If the trouble is due to a bad or missing drive, “Offline” will appear next to the drive.
Clicking the Rebuild button will prompt Mac OS X to review disk inconsistencies and repair arrays degraded due to inconsistent data. If a drive no longer mounts and is missing, highlight the missing or failed drive and click the - icon, then drag the replacement drive from the left-hand pane to the right-hand window, and then click the Rebuild button to repair the array.

I appreciate the assist, I got it back up and running, that wasn't an issue exactly. My big question is, what if I'm not around and one of the two disks fails again. This mini isn't even 3 months old and one drive failed already... I was hoping for some redundancy but if I'm essentially doubling my failure rate by mirroring then it's exactly the opposite... This is exactly why all my windows servers are running raid6 but I can't put more drives in the silly mini...

 

[mwroobel]

I appreciate the assist, I got it back up and running, that wasn't an issue exactly. My big question is, what if I'm not around and one of the two disks fails again. This mini isn't even 3 months old and one drive failed already... I was hoping for some redundancy but if I'm essentially doubling my failure rate by mirroring then it's exactly the opposite... This is exactly why all my windows servers are running raid6 but I can't put more drives in the silly mini...

Personally I am not a fan of the inbuilt RAID1 functionality of OSX (and therefore don't use it). When I need to do basic R1 in MacOS, I recommend using Softraid (or for more full-featured RAID I suggest using an Areca card (Not an option in anything but a MacPro unfortunately). I have seen situations where a broken R1 will fail to boot, generally you just have to boot OSX from DVD/USB and go to disk utility, add a new drive or re-add the existing one (depending on reason for the mirror breaking) and then rebuild.