Re: HA overhead

   I bet it wasn't the disk as much as it was the Disk controller and the
   amount of Cache that the controller had (In the example below of the 810,
   I would bet they installed new 2757 disk controllers with the 35GB
   drives).  We have done some performance tests on various configurations,
   and have found the new disks and controllers to be extremely quick.  You
   can even see a good performance improvement when you just keep the same
   disks and change the disk controllers.

       Speed of disk does make a difference, but the amount of cache on a
   disk controller will make even more of a difference.

       Pete Massiello

   oliver.wenzel@xxxxxxxxxxxxxxxxxxxxxxx wrote:

 Hello,

  

 Any ideas what the overhead would be running one of the major HA
    

 solutions?
  

 We have a 740 with aprox 350 gb used.
    

 About a year ago, we implemented DataMirror's HASuite (which basically
 uses remote
 journalling).

 Our 820 was quite busy before that, and with the additional journalling
 load performance
 went down the drain. Even putting the journalling on a second ASP didn't
 help much.
 We had to remove one of our apps (EDI) from the journalling, then it was
 okay.

 The problem was DASD usage, the disk were heavily contended with greater
 40% usage.

 We now have an 810 (with about 50% more CPW) with the newer 35GB drives,
 and only one ASP.
 Still, fully journalling all the stuff is no problem now!

 So, I guess it depends on your DASD setup. If you have older drives like
 6718 and below,
 and only 1 ASP, you might run into major problems.

 HTH,

 Oliver
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