Subject: Re: VPS mailing list, BSD interest?
To: Justin T. Gibbs <>
From: Jason Thorpe <>
List: tech-kern
Date: 10/01/1996 11:06:17
On Tue, 01 Oct 1996 09:53:02 -0700 
 "Justin T. Gibbs" <> wrote:

 > Actually, I don't think it is.  CCD should be relying on information stored
 > in a private area of the disk to determine what stripe sets what partitions
 > belong to, etc.  This is how all of the industrial strength filesystem VM
 > systems work.  When you open the partition, you see it has a CCD block 
 > on it, and then pass it on to CCD informing it of the dev that the block
 > came from.  The upside to this is that you can re-arange your disks (even
 > put them on different controllers) and the system still finds your array
 > and makes it work.  Having my root FS on a RAID 5 device makes it
 > more robust than having it on a single disk. This is more than enough
 > justification for allowing you to do this.

Just where do you propose to keep this information?

(Hint: it's going to be machine-dependent.)

When you say "open the partition", which partition are you opening?

(Hint: if you're opening /dev/sd0a, then you have to put all kinds of
crap to find the "ccd block" in the SCSI disk driver, and the IDE disk
driver, and the Xylogics disk drivers, and...)

How does the way the ccd is configured not allow you to move your
disks around (to different controllers, etc.)?

(Hint: it doesn't.)

Jason R. Thorpe                             
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