Re: "Enhanced" MD code avaible for review

From: Jeff Garzik
Date: Thu Mar 25 2004 - 19:57:04 EST

Justin T. Gibbs wrote:
None of the solutions being talked about perform "failing over" in
userland. The RAID transforms which perform this operation are kernel
resident in DM, MD, and EMD. Perhaps you are talking about spare
activation and rebuild?

This is precisely why I sent the second email, and made the qualification
I did :)

For a "do it in userland" solution, an initrd or initramfs piece examines
the system configuration, and assembles physical disks into RAID arrays
based on the information it finds. I was mainly implying that an initrd
solution would have to provide some primitive failover initially, before
the kernel is bootstrapped... much like a bootloader that supports booting
off a RAID1 array would need to do.

"Failover" (i.e. redirecting a read to a viable member) will not occur
via userland at all. The initrd solution just has to present all available
members to the kernel interface performing the RAID transform. There
is no need for "special failover handling" during bootstrap in either

hmmm, yeah, agreed.


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