hardware mirrors recognized as individual disks in fbsd

Ivan Voras ivoras at fer.hr
Tue Jan 16 21:51:28 UTC 2007

Steve Franks wrote:

> I want two 160GB mirrored volumes, not 4 unmirrored ones.  The RAID is an
> ASUS P5DR1-VM motherboard with a ULI raid chipset onboard.  Very nice setup
> for the money.

I don't know about the chipset or the controller, but judging from the
symptoms it's highly likely you actually have a soft-RAID controller,
and the actual RAID stuff was done by your Windows driver.

**IF** the driver was benign enough, you could *maybe* reconstitute a
mirrored volume with FreeBSD's software RAID driver, gmirror.

See the man page for details, but a command like "gmirror label mydisk
/dev/ad4 /dev/ad5" will create mirrored device /dev/mirror/mydisk which
you can then try to mount (actually if it works you'll see individual
partitions like /dev/mirror/mydisks1, etc.).

1. The above command will overwrite the last sectors on both drives with
its data (which you'll have to clean if you don't want the mirror
anymore). Usually they are unused but maybe the Windows driver used them
so you won't be able to use them under Windows.
2. Be very very careful - if this doesn't result in a valid mirrored
drive or the Windows driver did something unusual or nasty, you might
destroy the data by writing to the mirrored drive (just reading it will
not cause any damage). Mount the drive read-only first, and check you
can see valid data. Be absolutely sure before mounting it read/write
(and be careful about mounting NTFS read-write anyway - it's not risk-free).

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