Hot answers tagged raid
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The Apple provided Disk Utility (and diskutil shell command) will allow you full RAID control over internal and external drives. You do have to erase the drives to add the RAID capability, but then you can join those drives into RAID. That is the only potential drawback to implementing RAID storage on the Mac.
Drive spanning, JBOD, striping and mirroring ...
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Yes, RAID 0 is faster than using the drives independently of each other. Whether or not its noticeably faster depends on what kind of application you're looking at. Some setups benefit hugely from a RAID 0 setup, while for others, its pretty marginal.
There's also the convenience of everything being treated like one big drive.
I will however say that ...
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I think you should be fine. I upgraded to Lion on a Mac Pro that has a RAID 0. While the OS is installed to an SSD, not RAID, Lion still detected the RAID just fine. That's obviously a different scenario than what you have, but as the software RAID is handled at a higher level than the OS, I think you should be fine.
Obviously, have a backup ready to go ...
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In the end I went with the most expensive but also the fastest option: #1 which was the Mercury Accelsior PCIe based SSD hardware RAID array (RAID 0 by default which I will keep) in a Mercury Helios Thunderbolt PCIe chassis. The main reason was because it was the only one that mentioned it was bootable (and made a big deal out of that fact).
I paid $799 ...
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Both use the same data structure to create a volume within a volume.
One creates a wrapper and the data that is on the disk is scrambled / mapped through a cryptographic function so that the same data written to two different blocks ends up physically different on the drive. That's FileVault 2.
The other creates a wrapper and the data on the disk is either ...
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My guess would be that Apple prefers to have one drive handle only write processes as a backup and read/write from whichever one it considers the main drive. As to why this is, I have absolutely no clue. Seems kind of like a big oversight on their part. I've always kind of gotten the feeling that software RAID is pretty low on Apple's priority list.
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Disk Utility will only support RAID 1 and 0 using software raid.
If you have the RAID Card for the Mac Pro, you can configure RAID 5. I've never actually used or configured one of these in the wild so I can't give you exact specifics on using it.
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You're thinking of RAID-1 in the wrong way. RAID-1 is not an architecture intended to happily use a single surviving drive within a raid-1 group, and work out mirroring content later. Ultimately it will do that, but that is considered a recovery operation from a failed state, and it will destructively overwrite the mirror drive after replacement. In RAID-1, ...
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Firstly, RAID shouldn't include your backups. Something catastrophic hitting one, will hit the other. Eg. fire, burglary, etc.
Ideally, you want to keep one set off site. Using the 2 disks you can keep one at a friends, and sync the up periodically. There are tools that allow you to do this. Alternatively, something like BackBlaze, Amazon Glacier, will give ...
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I was unable to find how to rebuild the RAID from disk utility after a couple of hours of research. However, I managed to do it from the command line.
sudo diskutil list // to get a list of disks. Note the disk number of your new disk (e.g. disk4)
sudo diskutil appleraid list // note the uuid of the raid in question
sudo diskutil appleraid add member disk4 ...
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First let's clarify one thing: RAID is not the same as backup. Building a RAID array out of several (presumably USB) external drives would have many drawbacks. See this question I asked a while back for the explanation. I suspect what you really want is passive and seamless disk/data backup in which case OS X's built-in Time Machine works great. And if you ...
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You can setup a RAID 1 mirror over FireWire and connect the internal/external drives. However, I wouldn't recommend it.
First, you'll need the same size drives to do the mirror. Second, the speed of both drives will be limited by the type of connection to the external drive, so if its USB, the computer will run at USB speeds. If you are just using this iMac ...
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In this situation, I recommend using disk utility to partition the larger drive such that one partition matches the size of the smaller drive. Then setup the partitions of the same size as a RAID1. You will end up with a mirrored partition of 1.5TB and another un-mirrored partition of 0.5TB based on your first example.
Same thing will work for a 2TB + 3TB ...
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A mirrored RAID would operate only as fast as the slowest drive in the setup. In this case, unless you are using thunderbolt I imagine the performance would be awful. Another reason not to do a mirror with an external drive (if Disk Utility would even let you) is it'd be too easy have the mirror fail for a number of reasons.
I would use Time Machine to ...
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Well you already have a pretty optimal setup. Having the two disks in RAID-0 as your boot drive gives you the greatest possible performance. Just be sure to keep a good backup, since if either disk fails you lose the whole array. Superduper! is great since it makes a bootable backup for you, unlike Time Machine. I highly recommend it.
Otherwise you're good ...
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Enabling a RAID is destructive to the existing data using disk utility and native OS X tools.
You will need to have a temporary copy of the data to re-load it onto the new RAID volume.
I know several people that always set up their externals to be in a RAID so they can always mirror up existing drives after the fact to duplicate, snapshot or extend/stripe ...
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