>>>>>>It's worked well for me; I've had 3 complete drive failures of WD Caviar Black 1TB drives since Feb. 2010, but zero data loss from any of those failures.
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>What are you doing with those drives to get so many failures ? Making eggs sunny side up on ;-)

Probably babying them too much :-\ They're in an Antec P183 case, in the bottom drive cage, nicely separated, mounted on silicone shock-absorbing grommets, with a nice steady, filtered, room-temperature breeze blowing across them. Powered by an Antec CP850 PS and an APC UPS.

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>>>PMFJI. You said that most desktop motherboards support hardware RAID directly. What if most work is done on a notebook? Do you know if some notebooks support it too?
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>>With laptops the main issue is physical space in the machine for a second hard drive, and power and data connectors for it. I believe some large, high-end "gaming" laptops can include 2 hard drives. In those cases I've seen 2 possibilities:
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>>1. One drive is a relatively small but fast SSD for boot, OS and swap file. The other is a large capacity mechanical drive to store all of a gamer's "stuff"
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>Most 17' and some 15' have room for DVD, HD and spare bay. Some 18' have room for DVD and HD and 2 spare bays.
>Some Intel boards also give you the option of configuring part of the disks as RAID1
>(secure and sometimes read-faster, if reading is done by interleaving disk/sectors)
>and the rest of the disks either as RAID0 (even faster, but unsecure) or JBOD.
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>As Laptops are even more likely to get stolen, I'd rather opt for SSD + HD,
>if only 2 bays are available (you have to synch/backup IAC)

From what I gather, if you want to have 2 HDs in a laptop you pretty much have to order a machine that comes from the factory with 2 HDs already installed. If you don't, they'll give you a motherboard that doesn't have headers/connectors for secondary HD power and data, and/or you'll get the non-RAID version or get a BIOS purposely crippled so it won't support more than one HD. It wouldn't cost much to include the capability, but price pressure in that market is so fierce they'll save a few bucks wherever they think they can get away with it.

One trap the unwary can fall in is confusing partitions/volumes with actual separate physical drives. With some makers you can order a machine with, say, 1x 250GB drive, or 2x 120GB "drives". With the latter, you're still getting the same single physical 250GB hard drive, but they partition it for you into two 120GB volumes :( No RAID1 or performance benefits at all.

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>>2. Both drives are large-capacity mechanical drives configured as a RAID0 array ("high-performance" but unsafe)
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>>Any laptop motherboard that supports dual internal hard drives *probably* supports RAID1. However, in either case above you'd have to do major reconfiguration to implement RAID1.
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>Even with RAID0 just adding an empty disk to a full one does not give you any perf boost without rearranging files ;-)
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>>With RAID1, the redundant array capacity is the size of the smallest drive, so normally you use two drives of the same size. They should also have similar performance, in case 1 it would be a really bad idea to RAID1 a small SSD with a large mechanical drive. You'd need to replace one or the other. Case 2 already has 2 drives of the same size and type, but would require that they be wiped and reconfigured to RAID1 from RAID0, then reinstall everything. Some advanced imaging software might be able to image the RAID0 array and then resize it downwards to fit on the RAID1 configuration but I wouldn't bet on it.
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>Going for any RAID on different disk manu types is asking for trouble IMHO.
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>>If your laptop has a high-performance external connector (USB 3 or eSATA 6Gbps) then I believe there are some external enclosures that can hold two or more drives configured in various RAID flavours. USB 2 is not fast enough; eSATA 3Gbps might be OK but is uncommon on laptops.
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>You might just try with the external disk - most work places have enough boxes,
>so I try to get by with just external disc in breast pocket ;-)

Actually, these days, with a SATA 6Gbps or USB 3 port and a fast SSD in a suitable external enclosure, you could "just get by" very nicely indeed :)