View Full Version : mdadm and RAID5 - General Use Guide?

19th April 2006, 08:44 PM
I've recently setup a nice little system for the purpose of running a RAID5. I have FC5 installed on a small PATA drive and then I have 4 x 250 GB 7.2K RPM SATA drives. The drives show up without issues at /dev/sd[abcd] and all of the hardware is fully supported and recognized.

In a matter of minutes I successfully created a 750 GB RAID5 at /dev/md0 then formatted it and mounted and such. Dealing with disks under FC5 feels incredibly crude compared to OS X, but then again OS X doesn't support software RAID5. (Are there any applications I'm missing that provide comprehensive drive management? Everything I've found so far seems rather... non-robust.)

However, before I can start using the RAID I have to feel very confident that if a drive fails, the RAID continues to work, and that I can successfully rebuild the RAID. So I decided to take a drive offline. All I/O activity instantly stopped on the entire RAID. I played around with mdadm and never quite determined what happened. I tried again and I haven't had a lot of luck working with rebuilding and reactivating the RAID after a failure, without reformatting.

I'm curious if there's a clear, practical guide anywhere for working with mdadm. The man pages aren't cutting very well. Making a RAID isn't the issue; it's managing and resurrecting a damaged RAID that concerns me - basically what happens when it breaks. I can't risk making any mistakes during this process, otherwise I'm going to lose several hundred GBs of data. I want to understand this process 150% and practice a bunch.

If there's not a guide, could anybody perhaps offer some direction here?

19th April 2006, 10:25 PM
I have a RAID 1 (2 drive) setup that will boot off either drive with the other powered off. I have no experience with RAID 5 so I dont feel qualified to offer opinions. If nobody bites here you might want to try the mail list: