Hideki A. Ikeda (HidekiAI) [池田英紀] ["Tony" Ikeda] – BLog

Not to sound bitter but IMHO, RAID0 is useless.  Especially in today’s technologies where

• You can buy a terabyte drives if you need to have a large volume for a reasonable price
• Both Microsoft and Linux can “mount” another drive as a folder

RAID0 is just a method to connect more than one drive as a single volume back in the days when there were no large drives.  You can also extend the single drive paradigm (in *NIX, it would be based on “/” while Microsoft would be “C:\”) by mounting the new drive as a folder (i.e. “C:\Data” or “/usr/portage”).

Now on the other hand, you need the capabilities to have the folder size “grow”, at least for Linux, we have LVM2.

Now rather than having to backup your important data (such as SVN source, your www data, SQL data, personal source codes), why not make those important data into RAID1?  In my opinion, if you’re allocating a separate “physical” drive just for backup, having another drive just mirror using RAID1 is about the same investment.

If a drive goes corrupted/bad/none-functional on RAID0, you’re hosed on loss of data.  You swap out that bad drive and the contents goes with it.  With RAID1, at least you will get it re-mirrored and off you go, no data loss, only small time lost.

Just a thought…

Incidentally, have you ever got this message when you run mdadm:

mdadm: Cannot open /dev/xxx1: Device or resource busy
mdadm: Cannot open /dev/yyy1: Device or resource busy

Where xxx and yyy of course are your devices.  In most cases, it’s because you’ve booted your kernel with domdraid enabled.  If you are running grub, just edit your kernel options and remove the domdraid and you should be able to run mdadm without any issues.  Also, keep monitoring your /proc/mdstat until all your raid devices have completed its mirroring.  Oh, and let’s not forget that if your /etc/mdadm.conf does not contain the ARRAY settings, your devices (/dev/mdX) will never be defined.

Speaking of which, also, if you’re using dmraid (i.e. rc-update add dmraild boot) method, you should never have the kernel option of dodmraid, or else your devices will never be recognized.

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