Re: Virtual IOPs and CPU usage

[Larry Bolhuis <lbolhuis@xxxxxxxxxx>]

IBM has been slowly moving away from IOPS for quite some time now toward 
cards that are driven by the CPU directly. Based on that it is extremely 
unlikely that they would create any special hardware anywhere to handle 
virtual IOPs and IOAs. Considering that they work on machines as far 
back as model 6xx it must be true.  So these things don't really exist 
and are handled by the main CPU of the system, therefore if you make 
significant use of them you may add some CPU load. However consider what 
you are doing with them and you'll likely see the I/O load is what's 
really impacted. For example virtual tape usage drive huge I/O loads to 
the disks containing your virtual tape images. It's unlikely the CPU 
utilization to send the data is significant - remember all the virtual 
stuff is memory to memory (Virtual LAN, virtual Optical, Virtual Tape) 
it's all in the DASD I/O where the things truly add load.

 - Larry

qsrvbas@xxxxxxxxxxxx wrote:
> Not too long ago, the IOPs and other secondary processors in AS/400s 
> were commonly thought about as being part of off-loading some 
> processing from the main system CPU(s). Do any of you out there have 
> ideas about how virtual IOPs might make a difference?
>
> As many thoughts as I have about what a "virtual IOP" really is, 
> there are one or two aspects that aren't really clicking in my 
> picture of one.
>
> Tom Liotta