--- Paul Raulerson <[EMAIL PROTECTED]> wrote: > Hey Dave - > (Also speaking for myself) I agree with you in part. > But add 100 users to a PC and watch what happens to > the IO. Or add a heavily used database with a few > hundred users. PC Servers just do not scale in terms > of I/O the same way. iSCSI and other technologies > are starting to change that, but... > -Paul >
I would like to disagree. Our busiest servers, i/o wise is our mail server. It normally runs around 1000 concurrent connected users. It does slow on busy days, such as the first day after a holiday period, when users have a few hundred e-mails to process. I did investiagate and found the bottle neck is either the SAN switches or the SAN proper. That is the same SAN and Switchs that the mainframe uses. The reason they slow is beacuse of the way the I/O is designed in the SAN, that is down to a price not up to an commited I/O bandwidth and throughput. We recently upgraded the SAN and saw a significant improvement in both Mainframe and PC operation. A quick question. Do users with Sharks dedicate them to their Mainframes? or share with PCs? > > > From: "Dave Wade" <[EMAIL PROTECTED]> > To: IBMVM@LISTSERV.UARK.EDU > Date: Thu, 1 Mar 2007 08:17:00 +0000 > Subject: OT:I/O in Emulated Mainframes (Was Re: PSI > story) > > --- "Jeff Gribbin, EDS" <[EMAIL PROTECTED]> > wrote: > > > With a small amount of trepidation (but inviting > > stomping from anybody who > > feels that I'm off-base here) can I remind folk > > that, on IBM mainframe > > hardware, MIPS aren't the whole story. There's > > channels too - and in an > > I/O-related situation their power needs to be > ADDED > > to the CPU power to > > come up with a realistic, "comparative MIPS" > figure. > > > > It's a very long time since I saw anything that > > indicated how much MIPpage > > is offloaded into the channels by a typical, > > "mainframe" workload but > > please remember that, unless you understand how > > channels are implemented > > when comparing two different solutions, you can > > quickly mislead yourself > > regarding the genuine value of the, "MIPS" > > comparison. > > > > (I have a similar problem regarding, "channel > > bandwidth" - each individual > > channel on a mainframe might be, "slow" but > > potentially I can have several > > hundred running in parallel - in the right > > circumstances doesn't this give > > me greater capacity to work with than a single but > > much faster I/O portal? > > Do I want a firehose or do I want the Mississippi? > > As a man to whom I > > would happily defer when it comes to performance > > issues has occasionally > > been heard to comment, I think, "It depends ...") > > > > Regards > > Jeff Gribbin (Speaking only for himself.) > > > > Jeff, > Hercules runs channel emulation and CPU emulation > in > separate threads, so in a multi CPU box with say "n" > CPUS, if you define "m" Mainframe CPU, "n-m" are > generally (pedants note generally) free for channel > emulation. However whilst I have never tried to do a > real benchmark, I am firmly convinced that I/O is > not > an issue on a modern PC. > > To expand a little, I have tried a few simple things > to drive the I/O system up and bottleneck the I/O in > Hercules.. Sadly, every time, I have failed. I do > keep > trying, but I have never been able to justify adding > RAID, SATA, or even SCSI (other than for tape) to > the > box I use for Hercules. When I look in PERFMON the > i/o > queue length and the i/o service times remain short. > As I only emulate one CPU and have (kind of two) on > the Hyperthreaded box, I see the second CPUs > utilization remains low. > > I have therefore concluded that emulating S/370 > channels does not tax the system. Again it might be > different for the XA I/O system , but I don't think > so. (In fact I think it may be simpler) > > Dave. > Also speaking for himself. > > > > ____________________________________________________________________________________ > Do you Yahoo!? > Everyone is raving about the all-new Yahoo! Mail > beta. > http://new.mail.yahoo.com > > > ____________________________________________________________________________________ Yahoo! Music Unlimited Access over 1 million songs. http://music.yahoo.com/unlimited
