Re: The case against LVM

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On Thu, 2007-08-09 at 18:58 -0500, Mikkel L. Ellertson wrote:
> Robert P. J. Day wrote:
> > On Thu, 9 Aug 2007, Rick Stevens wrote:
> > 
> >> Uhm, not exactly.  You get up to four primary partitions, one of which
> >> can be an extended partition.  Inside that extended partition you can
> >> have as many "logical" partitions as you wish.
> > 
> > i'm not convinced of that infinite limit:
> > 
> > http://www.justlinux.com/forum/showthread.php?threadid=150073
> > 
> > anyone want to clarify that?
> > 
> From what I understand, there are a max of 16 device entries created
> for a SCSI hard drive. (sdx and sdx1 through sdx15) So while you can
> have more partitions then that, Linux will not let you access them
> when using the SCSI code to access the drive. I believe it is a
> driver problem more then a udev problem.

Well, the "x" in your example can take the RE form "[a-z]+".  For
example, we have some storage arrays with, oh, 130 LUNs on them.  They
appear as /dev/sda[1-15] through /dev/sdiv[1-15]

As far as the partition numbers, that's based on the minor number of the
block device.  The formula is "(16 * drive number) + partition number".
The "16" is what limits it to 16 partitions (with partition 0 being the
same as the whole drive, e.g. "/dev/sda0" is the same as "/dev/sda").

"man sd" will show you the magic.

----------------------------------------------------------------------
- Rick Stevens, Principal Engineer             rstevens@xxxxxxxxxxxx -
- CDN Systems, Internap, Inc.                http://www.internap.com -
-                                                                    -
-                   To err is human, to moo bovine.                  -
----------------------------------------------------------------------


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