RAID 1 Questions

Hey folks,

Now I have no experiences of RAID solutions, however I figure a RAID 1 configuration would be good to integrate into my back up solution.

For the record I currently have an on site and offsite back up at present which would remain in place. However as an added layer I thought RAID 1 would work quite well, my query is:

If one drive were to be removed or fail and a second one put in, would the 1 remaining drive automatically copy to the second new drive? Could this be used in a rotation for offsite backups? Or would the replaced drive need formatting everytime?

Sorry if this is a silly question....I currently have a 27" iMac and looking at this:Icy Box

RAID is NOT a backup.

Numenorean wrote in post #15229925
RAID is NOT a backup.

Absolutely I understand that, hence me adding it as a layer, not as a solution. Due to my lack of experience I'm trying to find its possibilities. Such as swapping out drives to ADD to offsite backups.

Once a drive is removed from a RAID array, the array becomes "degraded". The RAID controller should somehow alert you and ask for a replacement. The array will continue to function with the remaining drive(s) but is in danger should another drive fail before the array is repaired.

When you install a replacement drive, the controller will rebuild the array with the new drive. This will wipe out everything on that drive and its usually a rather time consuming process. This process isn't automatic in my experience. When you connect the new drive, you have to tell the controller to rebuild the array with it. I haven't used that particular product though.

Even if you reconnect the original drive you pulled 5 minutes earlier, the controller will still rebuild the array onto that "new" drive. RAID controllers synchronize data between drives at the block level, not the file level. So it won't just update existing files. It wipes out everything to integrate it into the array.

Constantly degrading and rebuilding an array will result in lowered performance since you'll spend a great deal of time in rebuilding mode. That's not what mirroring was designed for. All RAID levels above 0 are designed to increase uptime and/or increase performance beyond what a single drive can deliver. If that's what you want, then mirroring your data is a good idea. If you want another backup, just add another USB drive to your backup routine.

mike_d wrote in post #15230093
If that's what you want, then mirroring your data is a good idea. If you want another backup, just add another USB drive to your backup routine.

Or maybe add a large internal drive and run an automatic backup at whatever frequency you like. I back-up to an internal drive every two days and to an external USB drive much less frequently. For my working data drive I use a pair of 2TB drives in RAID 1.

mike_d wrote in post #15230093
Once a drive is removed from a RAID array, the array becomes "degraded". The RAID controller should somehow alert you and ask for a replacement. The array will continue to function with the remaining drive(s) but is in danger should another drive fail before the array is repaired.

When you install a replacement drive, the controller will rebuild the array with the new drive. This will wipe out everything on that drive and its usually a rather time consuming process. This process isn't automatic in my experience. When you connect the new drive, you have to tell the controller to rebuild the array with it. I haven't used that particular product though.

Even if you reconnect the original drive you pulled 5 minutes earlier, the controller will still rebuild the array onto that "new" drive. RAID controllers synchronize data between drives at the block level, not the file level. So it won't just update existing files. It wipes out everything to integrate it into the array.

Constantly degrading and rebuilding an array will result in lowered performance since you'll spend a great deal of time in rebuilding mode. That's not what mirroring was designed for. All RAID levels above 0 are designed to increase uptime and/or increase performance beyond what a single drive can deliver. If that's what you want, then mirroring your data is a good idea. If you want another backup, just add another USB drive to your backup routine.

That's exactly what I needed to know, thanks for taking the time reply everyone, just have to way up the pros and cons. The raid drive would not be degraded often maybe every few months just to rotate.

Yep, mike_d nailed. FWIW I have been running a RAID 1 on my PCs for over a decade. Never had one of those drives fail, but should it ever happen Ill be ready

For my rMBP I have a RAID 1 set that contains all my documents, photos, music, movies..etc. For backup of internal SSD and the RAID 1 set, I use a 3TB Time Capsule. Another set could be to also do an offsite backup.

MCAsan wrote in post #15230838
For my rMBP I have a RAID 1 set that contains all my documents, photos, music, movies..etc. For backup of internal SSD and the RAID 1 set, I use a 3TB Time Capsule. Another set could be to also do an offsite backup.

How are you connecting the RAID to the rMBP?

thunderbolt

My ethernet cable adapter goes into one port on the LaCie 2Big Thunderbolt enclosures. The cable from my rMBP goes into the other. I get fast ethernet transport and fast disk transport to/from the rMBP. When I travel, I take the ethernet-thunderbolt adapter just in case I am in a location with ethernet..and no wifi.

When new ACDs are released next year, I plan to get one So the rMBP would connect to the ACD. The ethernet cable would go to a dedicated ethernet port on ACD. The LaCie drives would plug into a thunderbolt port on ACD.

mattyb240 wrote in post #15229956
Absolutely I understand that, hence me adding it as a layer, not as a solution. Due to my lack of experience I'm trying to find its possibilities. Such as swapping out drives to ADD to offsite backups.

RAID hard drives are never intentionally swapped in/out unless it is broken. If you're thinking of swapping a RAID HD on regular basis, you're doing it wrong.

morph2_7 wrote in post #15238110
RAID hard drives are never intentionally swapped in/out unless it is broken. If you're thinking of swapping a RAID HD on regular basis, you're doing it wrong.

Expanding an array is the only other reason to swap out a drive. Either way, I always hold my breath until the rebuild is complete.