>From my understanding, the current use *is* for paging, but only when the >paging load (as determined by RSM) becomes "too great" for DASD.
In my thoughts IPL'ing from the "Flash Express" would be more like how z/VM implements NSS (Named Shared Segments). Basically, there would be a "logical name" which you could put in the IPL screen on the HMC. This "logical name" would basically be SSD storage which contained what is currently in SYS1.NUCLEUS. Once copied into main memory, control is given to some specific location and it does whatever is needed to initialize z/OS. All of this without doing I/O. You would have IPL and NIP "in memory" super fast. I don't know how difficult this would be to write. The only time you'd write to the SSD for this process would be after doing maintenance which would affect this "image" on the SSD. If the z/OS people were very careful, they might even be able to develop a way to "patch" the "image" and only write "changed" pages back to the SSD. I.e. if only one module was changed, then only that part of the SSD which contained that module would be rewriting. From what I've read, reading an SSD does not wear it out. Only rewriting a location. Of course, thinking about this, I wonder why IPL & NIP cannot be improved by containing the same structure on an IPL volume and loading it from DASD in the same way. IBM seems very reluctant to change how IPL and NIP actually work. I don't know why. I'm sure they have their reasons. Perhaps making such an image possible would simply be too difficult due to what IPL and NIP currently do and how they do it. Hum, I could look at the MVS 3.8j source to see what is going on. Perhaps one of the Hercules groups has already done something like this. Also, most SSDs report under capacity. E.g. An SSD rated for 500Gb actually contains 600 Gb of memory. Also, there is not a 1:1 mapping of a logical sector number to a physical location on the device. The controller on the device does "wear leveling" and maintains what is basically a "number of times written" number for each "section". So when a given logical sector is written to, the controller dynamically maps it to one of the "least" used memory locations. This elongates the device's life time. -- John McKown Systems Engineer IV IT Administrative Services Group HealthMarkets(r) 9151 Boulevard 26 * N. Richland Hills * TX 76010 (817) 255-3225 phone * [email protected] * www.HealthMarkets.com Confidentiality Notice: This e-mail message may contain confidential or proprietary information. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of the original message. HealthMarkets(r) is the brand name for products underwritten and issued by the insurance subsidiaries of HealthMarkets, Inc. -The Chesapeake Life Insurance Company(r), Mid-West National Life Insurance Company of TennesseeSM and The MEGA Life and Health Insurance Company.SM > > Could you create IPL and Paging packs on these devices? In case of > exceeding SSD write limits and the devices fail, you would have > replace volumes on reqular volumes too. Of course, once you IPL you > the I/O rate should be fairly low, and paging packs should have very > low I/O. > -- > Mike A Schwab, Springfield IL USA > Where do Forest Rangers go to get away from it all? > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
