[Veritas-vx] Adding a third mirror piece - VxVM 3.5

[Doug Hughes]

On Wed, 21 Apr 2004, Ruddle, Dave wrote:

> Hello
>
> I have an FSC Primepower Solaris server running Solaris 8 and VxVM 3.5.
> I have a number of mirrored volumes created and I want to add a third
> piece to the mirror, but not enable it until a later date (about a week
> later) in order to prepare for a storage system upgrade.
>
> I have seen that you can add a mirror piece with vxassist but this seems
> to add the piece and enable it in one go, and I cant see a way to do
> these 2 functions seperately.
> Also, will I still need to edit the /etc/vx/bin/vxmirror file to enable
> it to use more than 2 pieces in a mirror, or is this change incorporated
> in VxVM3.5 ???
>

I wonder if it would be possible to create a snapshot plex (vxassist
snapstart) and then, at a later time, convert to a full mirror.
Or maybe, a snapshot is exactly what you are looking for? then you
run the snapshot to break it off to a volume for backup or whatever.
Then you run the snapback to attach it back to the original volume?
reads will not be satisfied from the volume when the snapstart is
finished. They will come from the primary mirrors, but it will be
fully synchronized with them. When you run the snapstart it will
start all the I/O and make it synchronized. Unfortunately I haven't
been able to find any way to convert a SNAPDONE state plex into
an ACTIVE plex short of taking it to 'failed' first which would
mean a double-synchronization. (vxmend off vol-02; vxmend on vol-02;
vxplex att vol vol-02

Do you want to avoid that I/O until the time of your choosing?

Otherwise, as somebody mentioned, you can always use vxmake to
construct the subdisk and the plex and then run vxplex att
to associate it as a third mirror whenever your ready (which does
the full synch at that time)

	Doug