I've been told that after the metattach command has been run and two
stripes within a mirror start to resynch that I should wait until they
are finished before doing anything else.

Is this true or just paranoia? I'm mirroring a really big partition and
it's taking quite a bit time; time I could be using doing other things
than just waiting.

Thanks,
Ben..

On 2006-10-03 17:28:32 +0100, "bozothedeathmachine" 
<bozothedeathmachine@gmail.com> said:

> I've been told that after the metattach command has been run and two
> stripes within a mirror start to resynch that I should wait until they
> are finished before doing anything else.
> 
> Is this true or just paranoia? I'm mirroring a really big partition and
> it's taking quite a bit time; time I could be using doing other things
> than just waiting.


Mostly paranoia.  You don't have any redundancy until the mirrors are 
synched, and the machine will be slow because it's doing a lot of I/O 
synching disks, but it will work.

What is often a mistake is to do what I usually do: set up system 
mirrors on several slices of the same pair of disks (root, var, swap 
etc) then ask it to sync them all at once.

--tim

bozothedeathmachine wrote:
> I've been told that after the metattach command has been run and two
> stripes within a mirror start to resynch that I should wait until they
> are finished before doing anything else.
> 
> Is this true or just paranoia? I'm mirroring a really big partition and
> it's taking quite a bit time; time I could be using doing other things
> than just waiting.

It's safe to do things while a resync is happening. Resyncs are meant to 
be "in the background" and should not hold up everything else on your 
server.

One procedural reason not to do anything on the disks which are 
resyncing is that it's a good idea to provide the resync as much IO 
capacity to the disks as possible so the resync is not slowed down.

/dale

Dale Ghent wrote:
> bozothedeathmachine wrote:
> > I've been told that after the metattach command has been run and two
> > stripes within a mirror start to resynch that I should wait until they
> > are finished before doing anything else.
> >
> > Is this true or just paranoia? I'm mirroring a really big partition and
> > it's taking quite a bit time; time I could be using doing other things
> > than just waiting.
>
> It's safe to do things while a resync is happening. Resyncs are meant to
> be "in the background" and should not hold up everything else on your
> server.
>
> One procedural reason not to do anything on the disks which are
> resyncing is that it's a good idea to provide the resync as much IO
> capacity to the disks as possible so the resync is not slowed down.
>
> /dale



It is helpful to have this line in /etc/system to speed syncs:

set md_mirror:md_resync_bufsz = 2048

The only downside to doing things while the sync is in progress
is that disk access and IO generally may be slow due to controller
saturation and of course the contention for the disks syncing.

..

Thanks for all of the replies!!!!

"bozothedeathmachine" <bozothedeathmachine@gmail.com> ha scritto nel
messaggio news:1159892912.868816.129760@i3g2000cwc.googlegroups.com...
> I've been told that after the metattach command has been run and two
> stripes within a mirror start to resynch that I should wait until they
> are finished before doing anything else.
>
> Is this true or just paranoia? I'm mirroring a really big partition and
> it's taking quite a bit time; time I could be using doing other things
> than just waiting.

Mostly paranoia. While resynching you can do anything else because the
mirror work are doing in background, the same happening when the mirrorr are
synched and data are copied on both slice.

The only reason that I see is to leave as much as I/O during resynch. And
the I/O is much faster in multiuser solaris instead single/user.

Cesare