I have a new home server I built this weekend with 4 x 320 GB Seagate Barracuda SATA drives. I am going to load my O.S. this week however I don't have a RAID controller so I would like to utilize 'Software RAID' via 'mdadm' package. My question is since this is a general home server with no specific function rather than hold my data reliabily and resonably fast, how do you guys recommend I configure my partitions for RAID? What level would be best with my 4 drive configuration? RAID5 or RAID10? Should I use a 3 drive RAID and use the 4th as a spare? Please let me know what you recommend as I don't have a lot of expertise with what is not practical or useless when it comes to Mdadm RAID.

Thanks!

Carlos,

Since you have no hardware raid card, you're software raid solution will require you to first boot linux, then the raid array is available.

This means that you'll have 1 drive with your Linux installation, then the other 3 drives (Raid 5) will be your raid array.

Of course, for availability, you could mirror your OS drive and then mirror your 'data' drive.

The very best way, of course, is to use a hardware raid controller, set up a Raid 5 array, using your 4th drive as a hot-spare.

-Mike

I am fond of RAID 5, where you get the best of all worlds: *size* and redundancy (and speed). I tend to have my operating systems on RAID 1 and the data on RAID 5 (i.e. you can do this with two physical drives and then buy a third 320 for the data, to have the min 3 needed for RAID 5); but, on a couple setups, I have two partitions on a RAID 5 (i.e. which might be like your situation, you have to pick one RAID setup, which I picked RAID 5).

As far as having spares, my take on it is only if you are afraid you won't be able to find a replacement drive in the future (i.e. same size/rpm/cache specs), but I say it's probably better to swap out all your drives in that case.

As far as having mirrored mirrors (aka RAID 10), that's some crazy overkill unless you are storing priceless home movies of your kids' first step, words, performance, etc.

Just get a cheap external drive (e.g. 1TB USB for $75) and do a backup and if either your RAID setup or the external drive dies, replaced said broken stuff.

The key is that RAID it's only helping your up time, so don't stress over it too much (as you can always get corrupted data). The best thing you can do is BACKUP your stuff (i.e. copy to somewhere else).

Also, spikemike, carlos can use "missing" and --create a degraded raid 5 out of the remaining 3 drives (with one missing slot), then copy his current drive over to the array ("man dd" and "man parted" for clues), then boot to that new (degraded) array (i.e. edit /etc/fstab), then --add the original drive into the degraded array ("man mdadm" of course). A lot of work, but good for up time.

Sorry but you can do an entire RAID before you load the OS. I can set my OS on a 4 disk RAID 5 or RAID 10 if I wanted. Was just asking which is best for basic use. I don't think hardware RAID controllers are the best as the controller fails, everything fails. Plus there is no active way to monitor your RAID from the OS.

Thanks for the suggestions. I will just do the following:

/dev/sda1 100 MB - RAID (bootable)
/dev/sda2 2 GB - RAID
/dev/sda3 320 GB - RAID

Do that same schema above for all 4 drives and then create my RAID:

/
/boot
Swap

Hi Carlos,

Just curious, but why did you make separate RAID partitions for /boot and /swap? And why did you use RAID level 1 for those?

Because /boot is where Grub lives. Grub doesn't support anything greater that RAID1. If you do RAID5 on /boot, Grub will puke unless you're running Grub 2 which I doubt...

Oh ok, that makes sense, thanks.

Why are you using RAID 1 for swap instead of sticking with RAID 5?