Questions about gmirror

[Ivan Voras]

Ravi Pokala wrote:
> (1) What is the procedure for swapping out a dead drive while the system is
> online?

If the drive and the controller support hot swapping, remove it, put a
new drive in and do:

# atacontrol reinit channel
# gmirror forget gm0
# gmirror insert gm0 /dev/newdrive

Not many ATA drive+controller combinations are hot-swap-able.

> (2) Say a drive dies as a result of a power event, and does not respond to
> probing during the subsequent boot. Once I swap out the drive, (how) can I
> get the system to re-probe, recognize the new drive, and start
> reconstruction?

Exactly the same as above.

> (3) Will the stock bootloader and kernel be able to boot from just ad6 if
> ad4 dies, or is ad4 special because it was the original boot drive? (Or is
> this a function of the BIOS?)

It's a function of the BIOS but once the kernel boots it will bring up
gm0 and proceed from there "as usual".

> (4) Say I have two identical machines Foo and Bar, and four identical drives
> A, B, C, and D. I insert drive A into machine Foo as /dev/ad4 and install
> 6.2-RELEASE. I then insert drive B into Foo as /dev/ad6 and mirror using the
> procedure described above. When mirroring completes, I shut Foo down. Can I
> then pull drive B out of Foo:/dev/ad6 and install it in machine
> Bar:/dev/ad4, install drives C and D as /dev/ad6 on both machines to act as
> new mirrors, and effectively clone Foo's installation onto Bar?

With creative use of "gmirror forget" and "gmirror insert", yes.

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