SUMMARY: one T3 mirroring another T3?

I've received a number of replies to this query, and it appears I'll have
to use DiskSuite to mirror across T3 arrays. I was hoping to avoid this
(since I'd like to keep all of the CPU cycles for the Oracle software this
server will be running) but that's life. 

My original message follows, and then I've included the replies I received,
with my comments.

Erwin Fritz wrote:
> 
> I have two StorEdge T3 arrays, one of which is an alternate master to the
> other. Both are connected to a SunFire 3800, running Solaris 8 (April
> 2001).
> 
> The master T3, which I'll call #1 in this message, is configured with two
> RAID-0 volumes, one with five disks and one with four. There are no hot
> spares. The second T3, #2, is configured the same way.
> 
> I would like #2's volumes to be mirrors of #1's volumes. So I'd like to end
> up with #1's first stripe being mirrored to #2's first stripe, and the
> second stripe of #1 mirrored to the second stripe of #2.
> 
> The documentation for the T3 operating system shows how to configure
> mirrors within a single T3. I can't find how to configure the mirrors
> across T3s.
> 
> I know I can do this trick with DiskSuite, but I'd prefer not to have to
> waste OS resources on mirroring.
> 
> Has anyone done this?

Doug Otto wrote:
> 
> to mirror across bricks you need software, either Veritas or Disk(not
> so)Suite

Wayne McCormick wrote:
> 
> Erwin!!!!!
> 
> I don't think this can be done...  without DiskSuite of course.
> 
> Is there a reason why you don't want to use RAID-5?  I find it fast enough for
> what we are doing (upwards of 11 MB/sec write).  BTW, we have 12 T3 partner
> pairs in production spinning just over 12TB of useable space on a 4800.
> 

I don't like RAID-5 for Oracle databases, as a general rule, because of the
write performance penalty you incur when the parity is being stored.

> According to the documentation, you cannot create a volume across disk trays.
> Well it's not specifically saying that, but if you look at the format of the
> vol add command:
> 
> vol add volume-name data undn-n raid n standby und9
> 
> So, you see, to create a volume across trays you would need to be able to do
> something like:
> 
> vol add volume-name data undn-n uxdx-x raid 1
> 
> Which is not permitted given the syntax of the command.  I know, it's not
> concrete proof, but that's my interpretation of it. :-)
> 
> I don't know if you have this manual, so I've attached it for you.
> 

I did have the manual, but thanks anyway. The manual doesn't address
multiple T3 arrays (except for mentioning partner grouping) as a single
RAID entity, so that's when I sought out the advice of this list.

> Later,
> Wayne McCormick


Christopher Ciborowski wrote:
> 
> Looks like you will need to mirror across the bricks with SDS or VxVM.
> 
> -Chris


Christophe Dupre wrote:
> 
> Hi,
> the T3 is able to do RAID only within one box as far as I know, so you'd
> have to use DiskSuite to bridge to two together.


John Marrett wrote:
> 
> I don't know that you can do this without disksuite/veritas (which is
> included with your T3).
> 
> Really you should do the mirroring internally or between the T3s.
> 
> If you find out otherwise please post a summary.


Yura Pismerov wrote:
> 
>         Aren't they already mirrored (synchronized) ?
>         You mention the one of them is master.

That refers to failover of controllers, not the mirroring of the actual
disks. Partner-grouping the controllers means both controllers can see all
disks on each T3.

-- 
Erwin Fritz
Gilbert Laustsen Jung Associates Ltd.