SUMMARY: SDS / SVM mirroring with different disc geometries

Mika Tuupola tuupola at appelsiini.net
Fri Feb 18 03:50:30 EST 2005


	First of all sorry for the late summary.

	Thanks to following persons:

	Dan Lorenzini <lorenzd_at_gcm.com>
	John Christian <john.christian_at_TheCReGroup.com>
	Chuck <steeler_dude99_at_yahoo.com>
	Michael Horton <Michael.Horton_at_acntv.com>
	Gary Chambers <gwc_at_ll.mit.edu>
	Tim Chipman <chipman_at_ecopiabio.com>
	Anthony D'Atri <aad_at_verio.net>

	and the anonymous:

	NO UCE <nouce_at_mighty.co.za>

	
	** THE SOLUTION **

	Majority of the mails suggested that one can relabel the bigger
	disk to have the same geometry as the smaller one. This could
	be done in several ways

	1) #format -> type -> other -> type in the geometry of the 
	   smaller disk 

	2) #format -> type -> other -> choose the smaller disk type

	3) using fdisk -G to get the physical disk geometry from 
	   the smaller disk and then fdisk -s to write it to the
	   bigger disk

	
	It was also noted the SVM mirroring will work as long as
	the mirror partition is a bit larger or exactly the same
	size as the original. I did want to avoid this since IMO
	this will lead to trouble in the future if the smaller
	disk fails. There is a good SUMMARY about this:

	http://www.netsys.com/sunmgr/2003-07/msg00296.html

	
	Since the server in question had already went to production
	I had hoped to solve this with minimal downtime. This does 
	not seem to be possible due to the fact the OS has already
	been installed to the BIGGER disk. If it was the vice versa
	there would not be any problem.


	Since Solaris 10 was released and I was anyway going to 
	upgrade to it I will be reinstalling the OS to the smaller
	disk. The try to relabel the big one. If that does not
	work SUN promised to replace the disk. 

	As a sidenote, the geometry of the bigger disk did not
	match anything Sun sells...



	** ORIGINAL QUESTION **

	I recently purchased a Sun Fire v20z server with two
	73GB scsi discs. All original Sun parts. After istalling
	the OS I was about to mirror the discs with Solaris Volume
	Manager. I found out that the discs are made by different
	vendors _and_ they have different geometries.

	This also means I can't duplicate the partition with the 
	usual:

# prtvtoc /dev/rdsk/c1t0d0s2 | fmthard -s - /dev/rdsk/c1t1d0s2
Partition 0 not aligned on cylinder boundary: "       0      2    00
4200768   2100384   6301151   /"

	I know I could create the partitions by hand and preferably
	make the a bit bigger than they are in the primary disk.
	I would like to avoid this. What happens if the primary
	disk fails?

	Are there any other options? The disc geometries listed
	below:


        Vendor:   FUJITSU
        Product:  MAP3735NC
        Revision: 0108

        * Dimensions:
        *     512 bytes/sector
        *     936 sectors/track
        *       4 tracks/cylinder
        *    3744 sectors/cylinder
        *   38346 cylinders
        *   38344 accessible cylinders


        Vendor:   SEAGATE
        Product:  ST373307LC
        Revision: 0007

        * Dimensions:
        *     512 bytes/sector
        *     720 sectors/track
        *       4 tracks/cylinder
        *    2880 sectors/cylinder
        *   49781 cylinders
        *   49779 accessible cylinders


-- 
Mika Tuupola                      http://www.appelsiini.net/~tuupola/



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