Archived posting to the Leica Users Group, 2008/08/23[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]
Nathan Wajsman writes: > > This whole thread has been quite interesting, as I have considered a > neater approach to external disks than the JBOD approach I use now. > So, going back to basics. I understand what Raid 0, 1, 5 mean. What I > would like is a Raid 1 or 5 solution with as much capacity as > possible, at a reasonable price, and able to work with my iMac (in > other words, no possibility for a Raid controller card, it must be > able to plug into one of the FW or USB ports and be controlled by > software). Does such a thing exist, or am I better off staying with > JBOD? A simple solution would be to build a software RAID 1 (mirror) using a pair of externally connected drives. You can just use the software that's included in OS X. Being up to date (10.5) is probably a good idea, I think that they've improved the software RAID over the releases. I think that firewire drives still have a slight performance edge over USB drives, but the idea would work with either (or even, gasp, a mix). You can even experiment with the idea using a couple of usb flash drives and learn what happens when one of the drives goes missing, etc..... In fact, I just did. Gary will get a chuckle out of the fact that I don't think that you should boot your OS on the raid if you do it this way :).... You should be able to start Disk Utility (in Applications/Utilities), and then in the big window select the RAID tab. Drag the firewire devices (or the usb disks, or the flash drives) into the window it calls the "list below", and make sure that the RAID type is Mirrored RAID Set. You probably want a Volume Format of Mac OS Extended (journaled). I was curious how it would handle the fact that you can't really plug in both devices at exactly the same time. A bit of experimentation with some flash drives suggests that after it sees the first half of the mirror it waits for a bit (a minute?) to see if the second half will show up, and if so it brings it up intact, otherwise it brings it up "degraded" using the first half that it sees. I just goofed around with it a bit, and I ended up having to use the diskutil command line rebuild discussed here: http://docs.info.apple.com/article.html?artnum=106987 after I intentionally messed up the raid. Came back just fine though. As I've said before, play with it before you trust it. I don't know what the performance implications of doing multiple devices over the firewire bus will be, but the OS should be able to keep a writes going to both devices in parallel pretty well.... I can also vouch for the readynas product. I have an NV+ and have heard good things about the newer devices. Performance won't be nearly as good but you can get much bigger w/ less futzing about. http://www.readynas.com/ http://www.readynas.com/?cat=13 (their "mac corner"). g.