Hardware Raid question

Karl Denninger karl at denninger.net
Tue Jan 18 12:11:51 PST 2005

On Tue, Jan 18, 2005 at 07:58:59PM +0000, Mike Woods wrote:
> > Why does the os even detect the individual drives when the raid card made it a
> > single drive and the os install is after the raid bios???
> Because the chipset provides means to control both single disks and 
> arrays thus you get both, just the way that card chose to do things :)
> -------------
> Mike Woods
> IT Technician

Question on this...

I noted that if I come up on the "fixit" disk, I can use atacontrol to
'create' a RAID1 array across two disks with ONLY the motherboard
IDE controller!

It also APPEARS to read/write to both disks - and if I disconnect one of
them, intentionally "failing" it, it also appears to do the 'right thing'
and keep running in degraded mode too!

However, a "rebuild" (once one 'replaces' the dead disk) instantly returns 
and does nothing.

Is it thus correct to conclude that the DRIVER abstracts the RAID1 function
internally, and that the only thing you lose is the ability to replace/recopy
the array?

That is, in the event of a failure you could dump the remaining (good) disk,
replace the bad, re-initialize the array and then copy it back - you'd lose
"hot" rebuilds, but not the inherent protection of the mirroring.

Am I missing something here?

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