Comment Careful, there's a gotcha with IDE RAID... (Score 3, Insightful) 597
...so be alert.
Each IDE controller can support up to two drives, a master and a slave. What happens if you hang two drives off one controller, and the "master" drive dies?
If it dies badly enough, the "slave" drive can go offline. Now you've got TWO drives in your array that aren't talking. There goes your redundancy.
If your purpose in using RAID is to have a system that can continue operating after a single drive failure, then you better think again before you hang two drives off any one controller.
As it points out in the Linux software RAID docs, you should only have one drive per IDE controller if you're really concerned about uptime. That would imply that "4 channel" RAID cards should only be used with a maximum of two drives, both set to "master", and no "slaves".
Note that this does not apply to SATA drives, as there isn't really a master-slave relationship with SATA -- all drives have separate cables and controller circuits. SATA drives are enumerated the same way as older drives for backwards compatibility with drivers and other software, but they are otherwise independent. (At least that's what I hear, I haven't actually seen one of these beasts yet...)
And of course none of this touches on controller failures, which is another issue. But if you are worried about losing drives and still staying up, then better take this into consideration when you design your dream storage system.
(I don't know about you guys, but I have lost several drives over the years, and not one controller...)
Each IDE controller can support up to two drives, a master and a slave. What happens if you hang two drives off one controller, and the "master" drive dies?
If it dies badly enough, the "slave" drive can go offline. Now you've got TWO drives in your array that aren't talking. There goes your redundancy.
If your purpose in using RAID is to have a system that can continue operating after a single drive failure, then you better think again before you hang two drives off any one controller.
As it points out in the Linux software RAID docs, you should only have one drive per IDE controller if you're really concerned about uptime. That would imply that "4 channel" RAID cards should only be used with a maximum of two drives, both set to "master", and no "slaves".
Note that this does not apply to SATA drives, as there isn't really a master-slave relationship with SATA -- all drives have separate cables and controller circuits. SATA drives are enumerated the same way as older drives for backwards compatibility with drivers and other software, but they are otherwise independent. (At least that's what I hear, I haven't actually seen one of these beasts yet...)
And of course none of this touches on controller failures, which is another issue. But if you are worried about losing drives and still staying up, then better take this into consideration when you design your dream storage system.
(I don't know about you guys, but I have lost several drives over the years, and not one controller...)
