Editorial: RAID nightmare. by Saeed Amen
One of my
previous editorial explained the principles of the RAID system. You can
run a pair of hard disks, either using RAID 0 for maximum performance
or using RAID other levels for data protection, like RAID 1 or RAID 5.
I ignored the need for data protection and plumped on using RAID 0. My
controller of choice was Promise FastTrack IDE RAID card. At eighty pounds
it did not offer many features, but it did allow me to get on the RAID
bandwagon. For the hard disks, I choose a pair of Western Digital 7200rpm
100 GB drives. Thus I had 200 GB of storage on my computer, quite a feat
given that I had spent less than five hundred pounds! Several years ago
you would have required many hard disks to create just 100 GB of hard
was a perfectly decent dual Athlon MP machine. Each processor ran at 1.2
GHz. One of the drawbacks of a cheaper RAID card (apart from the fact
most won't support RAID 5) is that it does not have an board processor
to handle IDE traffic. With two processors this was hardly going to be
a problem. Setting up the RAID array was easy enough. I first went into
the RAID cards bios and created a RAID 0 array. Once that was done, I
installed Windows (which required a floppy disk for the RAID card driver).
Troublefree operation ensued for several months. Data transfer rates were
phenominal. Using a hard disk benchmark program, made by Pinnacle Systems,
my computer clocked 70MB/s, a simply amazing figure. Then all of a sudden
the computer would not boot properly, as it kept on stalling whilst running
ScanDisk. I knew something was wrong, but left it, in the belief that
my RAID array would suddenly work! Then some Windows files became corrupted
and I could not boot up. I had install Windows on a separate hard disk,
and then access the RAID array through it. Luckily, it worked and I backed
up my important data on the RAID array to another computer. Formatting
the RAID array, and installing Windows on it, seem to solve the matter.
That was until the RAID array failed again. So I went the whole tedious
process of recovering the data and formatting it. Then it happened a third
time. On this occasion the RAID array was totally destroyed, the RAID
card wouldn't even recognise it! I eventually found the problem was in
one of the two hard disks, which I promptly removed from the computer.
I lost all the data on my RAID array, after I had done the last backup!
Although only one hard disk was faulty, using RAID 0, means that this
could be enough to lose the whole thing.
Now my faulty disk is being sent to Germany to be replaced under warranty
by Western Digital. In the meantime I am running the other 100 GB drive
on a bog-standard Ultra100 motherboard based interface. Once the other
drive returns from maintenance it is unlikely I'll create another RAID
array, and instead I'll just use it normally! True I'll won't get 70MB/s
transfer anymore, but hopefully it'll be more reliable. Basically if you
do plan to run a RAID array with IDE hard disks, which are a lot cheaper
than the traditional SCSI hard disks (which tend to be better built because
of the price premium), make sure you backup your data regularly, otherwise
you might have a RAID nightmare. No, replace the last statement, whether
you have a RAID system, or an ordinary IDE one, backup your data, with
CD-Rs at 20p you do not have an excuse anymore!