EMC presentation

I just got out of a presentation (sales job) from EMC, that they give us every 
year or two about how EMCs DASD is superior.   Presently we have multiple TBs 
of IBM internal ultra SCSI drives attached to 6532/6533 IOPs on multiple 
AS/400s, using the 40MB bus.  We also follow IBMs white paper for the number of 
disk arms per system, etc.  ***I have seen several opinions about EMC (good and 
bad) on this list and I am looking for businesses that have switched either 
way(IBM or EMC) due to support or performance issues (email privately if 
desired).  Often it is easier for some managers to understand a list of 
dissatisfied customers than explain all of the technical details.    The 
presentation was fun as usually since EMC brought in there "expert" from 
headquarters, and had three locals to support him.   Of course I had to correct 
the expert several times on ASP storage technicques and main storage processes 
on the AS/400. 

They stated that  when a page of data (4MB page) is written to any vendors DASD 
on an AS/400 that it reserves that track of DASD for only that file, so when 
future data is added to disk for that file it will be contiguous on disk.  This 
is why there "Track Cache" has a 60 to 85% hit ratio. I tried unsuccessfully to 
explain scattered storage to them.   Also they stated expert cache for 
mainstorage is usually not effective, *CALC ( however here we see up to a 70 % 
improvement on some batch jobs)  ***  What have others on the list seen with 
expert cache?    Although EMC DASD attaches to a 6501 which has a 20MB/sec 
transfer rate and IBMs DASD attaches to a 6533 which has a 40MB/sec transfer 
rate there DASD is faster? go figure.    Also I tried to explain even with if 
data was contiguous (of course it is not) most people use a lot of logical 
files to access data so it would be pointless to store data as such. ( Logical 
files confused them), etc., etc., etc.     We  invited them t!
 o do head to head test with our current DASD config.  Run batch jobs  on our 
test system using our current  IBM DASD and then switch to EMC DASD and run the 
exact same job mix.  Has anyone on this list performed a true head to head test 
such as this?  Thanks for your responses


Bob Marion
AS/400 Technical Support
Plano TX
EMail:  bob.marion@ps.net

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