SUMMARY: SDS / SVM mirroring with different disc geometries

From: Mika Tuupola (tuupola@appelsiini.net)
Date: Fri Feb 18 2005 - 03:50:30 EST


        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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