Radoslaw, That's true enough, and the MIPS would have to be factored in to the equation. But I would have to ask how much tape activity is happening during the MIPS peak that currently drives your CPU capacity? Is there enough tape activity for the compression MIPS to bring your next upgrade forward?
The majority of tape activity is usually backup and archive. It is not my experience to see a large number of tape backups running during the batch or online peak, and DFHSM archive activity is almost always scheduled during the CPU valleys. I rarely find tape jobs in the batch critical path, which makes them a workload that can run in service classes with relatively low importance. I implemented DFSMS compression for DASD in the past, and it did not have a huge impact on MIPS. I hear this is also the case for many IAM users, as well as some of the ISV compression products. I expect VTFM would be similar to these products. Yes, compression will use some extra CPU time, but the cost is measured in how it affects your upgrades. Ron > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On > Behalf Of R.S. > Sent: Tuesday, 15 May 2007 7:29 PM > To: IBM-MAIN@BAMA.UA.EDU > Subject: Re: Virtual tape limits (Was: OEM software electronic download > report card) > > Ron Hawkins wrote: > > Mark, > > > > A few problems I see with this article: > > > > 1) They purchased the tape libraries based on 2:1 compression and the > SATA > > with zero compression. Virtual tape software will compress the data on > disk > > at the same rate as tape. > [...] > To be fair... AFAIK the compression is made by CPU. *Mainframe CPU*. What > resoucre is more expensive ? > I know some installation (few dozen Terabytes) of virtual tapes on disk. > The most expensive DASD is used to waste the most expensive CPU cycles and > store the least important (from the performance point of view) data. > Just my observation, I'm not biased to any vendor solution. > > -- > Radoslaw Skorupka > Lodz, Poland ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
