[CentOS] Re: IDE RAID support -- clarification ...

Fri Jul 22 12:51:10 UTC 2005
Bryan J. Smith <b.j.smith at ieee.org>

"Bryan J. Smith" <b.j.smith at ieee.org> wrote:
> ??? I thought XP Pro can use LDM and striping/mirroring, just
> like Windows 2000 Pro ???

Just FYI, you have to use a Logical Disk Manager (LDM)
Disk Label** (aka "Dynamic Disk") to use the software RAID
features of Windows 2000 Pro and XP Pro (not sure about
XP Home, what it offers).

This is a safety feature, as legacy BIOS/DOS Disk Labels
(aka "Basic Disk" -- i.e., old Primary/Extended/Logical
disk slices) can store inter-Disk Slice** dependencies/
associations.

LDM Disk Labels show up as a Disk Slice of type 42h in a
legacy BIOS/DOS Disk Label.

It's the same reason why you should use a Logical Volume
Management (LVM) Disk Slice when you use Linux's Software
RAID, even when using the Multi Disk (MD) for your RAID.
It will store Disk Slice associations, unlike a legacy
BIOS/DOS Disk Label.

-- Bryan

**NOTE:  I'm purposely using established UNIX terminology,
instead of PC:  
  Disk Slice ~ Partition
  Disk Label ~ Partition Table

Disk Labels can be encapsulated inside of Disk Slices.  E.g., the
"Extended" primary partition is really a new Disk Label (with
"Logical" partitions) inside of a Disk Slice.  Same deal with BSD
Disk Labels, NT5+ (2000+) LDM Disk Labels, Linux LVM Disk Labels,
etc...  The legacy BIOS/DOS Disk Label has 0 storage other than
the Disk Slices themselves (other than MBR and the partition
table itself -- no meta-data, no journal, no geometry, etc...).


-- 
Bryan J. Smith                 mailto:b.j.smith at ieee.org
Sent from Yahoo Mail (please excuse any missing headers)