Pete wrote:
[ ... ]
I thought Vinum was FreeBSD's RAID system.  If you wanted to do software
RAID with FreeBSD, you needed to use Vinum.  Now I find this out.  Does
that ATA subsystem have RAID support built in?  (Since atacontrol just
seems to control the ATA devices...)  If this is so, what's the use of
Vinum?  When should I use one vs the other?  How do Vinum and the ATA
subsystem's RAID relate?

Vinum resembles a popular commercial RAID product called Veritas LVM; vinum does software-based RAID. The ATA RAID support via atacontrol apparently requires hardware RAID controllers like the Promise or Highpoint devices. Hardware based RAID is likely to be faster, particularly in the case of parity calculations for RAID-5. (Not that many IDE controllers can do RAID-5, but...)

The RAID volumes created with vinum are accessible only under FreeBSD, whereas the ATA-based RAID solutions create a logical volume accessible via the normal BIOS interfaces, so the RAID device looks like a single, bigger physical disk drive. Thus you can use an ATA-based hardware RAID volume as a boot device, install multiple operating systems, etc.

Generally, one cannot boot from a vinum based-device, unless you are only doing RAID-1 mirroring. I'm familar with something called "encapsulating the root partition" under Solaris and Veritas; it's not for the faint-of-heart. :-)


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