Yes, I know it and I support it. But be aware that I can not see the result of the READ_COUNT because I take control before the IO is really done to the real device.
Shai On Mon, Nov 1, 2010 at 12:27 PM, Rick Fochtman <[email protected]> wrote: > ---------------------------------------<snip>----------------------------------- > > > A few words on replication. >> >> The standard replication is sending CCWS to all controller which >> have mirrors disks. Sometime controller send data to other controller to >> sync the data between all of them. >> In this process each controller emulates the CCWS and by that create the >> same data as the source disk. In this case the search key is very easy to >> implement. >> >> MFNetDisk because of the slow media of TCP do something else. It is >> analyze >> the CCW in memory without accessing the source disk data. That is why it >> is >> hard to process the search key without access the data in the disk. After >> process the CCW it is decide what tracks need to be ReSync in the mirrors >> of >> the source disks. This process is complicate process especially for search >> key CCW. Using this processing, MFNetDisk never block the real disk but >> the >> minus is that this is ASync processing meaning that if there is crash in >> MF, >> the mirror may be not fully Sync with the source disk. the MFNetDisk >> replication can be good if you want to create Sync point or backup of the >> real disk in specific time where you can validate that the process of >> ReSync >> is done completely without updating the source disks for short time until >> the ReSync is totally over. This is called Sync Point where the mirrors is >> fully Sync with the real disk. >> >> About the MFNetDisk emulation. Each CCW is sent to the PC which access the >> data in the emulate disks and easily can process any CCW include serach >> key >> and all other CCWS. >> >> > > -------------------------------------------<unsnip>------------------------------------- > Shai, it's entirely acceptyable to use a READ COUNT CCW before the SEARCH > KEY HIGH-OR-EQUAL CCW. > > READ COUNT > SEARCH KEY HIGH-OR-EQUAL > TIC *-16 (Back to the READ COUNT > READY DATA (or WRITE DATA, as needed) > > Rick > > > ---------------------------------------------------------------------- > 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 > ---------------------------------------------------------------------- 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
