Thread: RAID 1 question
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Old 2nd April, 2003, 11:39 AM
Aedan Aedan is offline
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Join Date: September 2001
Location: Europe
Posts: 13,075

If you remove one of the mirror drives, the mirror array is then broken (or degraded). At which point you've no longer got a mirror, but just a single disk.

Depending on the way the promise works, it may be able to rebuild the mirror on the fly. However, this is a fairly intensive operation, and the machine will operate much slower than normal until the mirror rebuild is complete. Obviously, the length of the mirror rebuild depends on how large the disks are!

Additionally, with hot swap IDE, you need more than just a hot swap controller. You need to ensure that each caddie is connected to a seperate IDE port. (Master/Slave is NOT allowable for a stable IDE hotswap). You also need IDE caddies that specifically support hot swap. The reason for this is that IDE drives are not designed for hot swap. As such, very careful control must be kept of the power and data lines, so that the power/data is sequenced properly. This just means that the ground is applied first and broken last, the power is applied second, and broken second to last, and the data is applied last, and broken first. Failing to do this could potentially destroy a drive and the controller at the other end!

Promise only claim hotswap is available when using their SuperSwap caddies. These caddies also do enviromental monitoring, so the controller is aware of the caddy temperature and fan speed.

Any views, thoughts and opinions are entirely my own. They don't necessarily represent those of my employer (BlackBerry).
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