Sorry, I should have called it Simultaneous Write feature, here is the info 
from the Admin Guide....

Simultaneous Write to a Primary Storage Pool and Copy Storage Pools
To simultaneously write data to a primary storage pool and one or more copy 
storage pools, you can specify a list of copy storage pools in a primary 
storage pool definition using the COPYSTGPOOLS parameter. When a client backs 
up, archives, or migrates a file, the file is written to the primary storage 
pool and is simultaneously stored into each copy storage pool. If a write 
failure occurs for any of the copy storage pools, the COPYCONTINUE parameter 
setting determines how the server should react. See Table 12 for additional 
information about storage pool definitions. 

When using copy storage pools for the simultaneous write of data to a primary 
storage pool and associated copy storage pools, be sure that all resources, 
such as enough drives, are available for the write operation. For example, each 
simultaneous write operation will need all of the volumes to be simultaneously 
mounted. This requires that the number of available drives must be equal to or 
greater than the number of volumes to be simultaneously mounted. For additional 
information, see Mount Limit and the REGISTER NODE command in the 
Administrator's Reference for information about the MAXNUMMP parameter. 

Note:
When defining copy storage pools to primary pools that have defined next pools, 
the copy pool list for each primary pool should be the same. Defining different 
copy pool lists can cause resources to be freed when using the next pool. If 
the resources are freed, it can delay the completion of client operations. 

-----Original Message-----
From: Sal Mangiapane [mailto:salm AT VITALDS DOT COM]
Sent: Friday, April 25, 2003 4:12 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: Will Hard Drives Edge Out Tape Drives?


> We currently have over 180 TB of data sitting on 3590 tapes, we have 2
> onsite 3494 ATL's 48 drives total, and 1 offsite (17 miles away) 3494
> ATL with 24 drives connected by dark fibre (all of the details escape me
> right now).  We primarily run our over 800 server classed client backups
> to diskpools nightly (2 TB worth), however, for our larger files
> (Exchange, SQL) we utilize the dual write feature and write about 1 TB
> of data to both locations simultaneously actually faster than we could
> to disk.  Now, before everyone starts to reply with all the possible
> disadvantages to this, trust me, we have taken those into consideration,
> and that is why we don't back everything up to tape directly.
>


What is the dual write feature?

--snip--

thanks and God bless,

sal