Tom and Co., I see no statement that there is any intent to combine the 3 existing disks. The note simply states that 3390-09s are to be created. If the existing disks, excepting the one that requires more space, are to remain where they are, there probably would be no performance hit if no other active minidisk is created on the large volume. If this is an already existing minidisk that is to be expanded, the existing use patterns would probably continue.
Regards, Richard Schuh -----Original Message----- From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On Behalf Of Tom Duerbusch Sent: Tuesday, April 25, 2006 9:32 AM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: 3390 Mod 3 verses 3390 Mod 9s If you were near the performance limits of your current (3) 3390-3 volumes, then you don't want to combine them to a 3390-9. To really know, you need to know the I/O rates on the 3 volumes. Also, you need to know what dasd you are actually using. Modern dasd (raid that is), with sufficient cache can really substain much higher I/O rates then we are use to thinking about. If this is for minidisks and not SFS, DB2 or Guests machines, minidisk cache will eliminate most of your concerns. A standard CMS user only does 1 I/O at a time. So if it is for just one user, don't worry about it. If it is for multiple users reading it, then MDC takes over. If you have multiple users writing to it, now we go back to the I/O load. Tom Duerbusch THD Consulting >>> [EMAIL PROTECTED] 4/25/2006 8:03 AM >>> I have a question that pertains to performance. We currently have 3390 mod 3 defined volumes. The customer requires a larger mini disk size than what will fit on a 3390 mod 3. We are planning to create 3390 mod 9s for their larger mini disks. Would someone explain the performance hit that will occur by placing their data on a larger volume. Maybe it is insignificant, but I seem to recall the architecture permits a limited number of accesses to the device. If there are a large number of users who require access at a given time, then the users could end up waiting for the device? Please advice. Thank you. Cecelia Dusha
