The tracks towards the center have fewer sectors than the tracks towards the rim.
Really?
From: "McKown, John" <[EMAIL PROTECTED]> Reply-To: IBM Mainframe Discussion List <[email protected]> To: [email protected] Subject: Re: Track size and maximum single volume data set size Date: Thu, 12 Jul 2007 12:08:23 -0500 > -----Original Message----- > From: IBM Mainframe Discussion List > [mailto:[EMAIL PROTECTED] On Behalf Of Ken Porowski > Sent: Thursday, July 12, 2007 10:48 AM > To: [email protected] > Subject: Re: Track size and maximum single volume data set size > > > Out of curiosity, what is the PHYSICAL track size of modern disk (EMC, > IBM, etc.). > Is there an industry standard or is everyone different? IIRC, many have differing sized tracks. The tracks towards the center have fewer sectors than the tracks towards the rim. > > I would think that there is still some validity to matching > I/O requests > to the PHYSICAL geometry even with emulation, RAID, striping, cache, > etc. Head movement must still count for something. Not really very much in Enterprise class DASD subsystem. They are generally configured with so much cache and advanced "read ahead" software that output is "write in" in the cache and so is independant of physical I/O. Reading can be affected, but the "read ahead" can usually help significantly. I think today's mantra is to simply have so much cache that the physical I/O is not significant to the response time of the subsystem. -- John McKown Senior Systems Programmer HealthMarkets Keeping the Promise of Affordable Coverage Administrative Services Group Information Technology The information contained in this e-mail message may be privileged and/or confidential. It is for intended addressee(s) only. If you are not the intended recipient, you are hereby notified that any disclosure, reproduction, distribution or other use of this communication is strictly prohibited and could, in certain circumstances, be a criminal offense. If you have received this e-mail in error, please notify the sender by reply and delete this message without copying or disclosing it.
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