MY QUESTION:
>ODS has the option to allow reads on a mirrored file system to always
>go to the first submirror. I'd like to use this feature to choose
>which disk will be read for each mirrored file system but I can't seem
>to control which submirror becomes the `first' submirror. In my case I
>have a md.tab file including:
>
> d107 -m d27
> d27 1 1 /dev/dsk/c2t0d0s7
> d17 1 1 /dev/dsk/c1t0d0s7
>
>As soon as I `metattach d107 d17' to add the second submirror the `d17'
>submirror becomes the first submirror (`Submirror 0') and `d27' becomes
>the second submirror. Nothing I do will allow me to have `d27' as the
>first of two submirrors of `d107'. The documentation is no help.
THE RESPONSES:
For once I had no useful responses from the net, only a `why would you
want to do that?' I put in a call to Sun support who, after some
experimentation, solved the problem!
THE ANSWER:
Under ODS, if you want to control which submirror is the first
submirror, you need to use the `-r' (read from the first submirror)
option when first using metainit on the mirror, e.g., in my case use
the following `md.tab':
d107 -m d27 -r
d17 1 1 /dev/dsk/c1t0d0s7
d27 1 1 /dev/dsk/c2t0d0s7
If d107 is already initialised, use metaclear on it (unmount any file
system first) and then metainit it (and the submirrors if necessary).
Finally, metattach d17. d27 will remain the first submirror.
The key here is to initially set up d107 with the `-r' option. Using
metaparam to set `-r' later did enable reading only from the first
submirror, but didn't allow control over which partition was that
`first submirror.'
-- James Ashton System Administrator VK1XJA Department of Systems Engineering Voice +61 6 249 0681 Research School of Information Sciences and Engineering FAX +61 6 279 8088 Australian National University Email James.Ashton@anu.edu.au Canberra ACT 0200 Australia
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