> -----Original Message----- > From: IBM Mainframe Discussion List > [mailto:[EMAIL PROTECTED] On Behalf Of Tom Marchant > Sent: Thursday, July 12, 2007 2:04 PM > To: [email protected] > Subject: Re: Track size and maximum single volume data set size >
<snip> > > Since most RAID arrays get their data from several drives at > once, you might > consider the size of a logical track to be much larger. > Don't forget that any > access method that uses TTR will be limited to 256 records per track. > > -- > Tom Marchant Well, that applies to everything, actually. TTR is relative, MBBCCHHR is absolute. In both cases the R is a single byte. Now, given IBM's love for 4K physical blocks for almost everything new, that would be 4096*256 = 1,048,576 maximum usable bytes per track,or 1MiB per track. That is about 18x the size of a current 3390 track. Of course, if IBM were to do this, without futher changes to DASD allocation, that would mean that the minimum allocation would now be a MiB per dataset instead of about 55K per dataset. Which may or may not matter with such a device. Use of a 4K logical physical block would "most efficiently" be emulated on current FBA disks by striping the data over 8 volumes, because currently a sector is .5KiB (512 bytes). This would maximize the effective transfer rate by doing 8 transfer simultaneously, if all the data paths are set up correctly. However, I have read that there is some industry mumbling about increasing the size of a sector to 4096 bytes. http://www.techworld.com/storage/news/index.cfm?newsID=5653 -- 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. ---------------------------------------------------------------------- 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
