spear@afwl-vax.UUCP.UUCP (02/13/87)
At the last DECUS (S.F.) there was a DEC person from the Large Systems Group or somesuch that was looking for user inputs on high-end storage devices to include semiconductor "disks". I asked him about the much-talked-about RAM-disk driver in STABACKIT.COM and he gave a surprising answer. This type of RAM disk can actually hurt system performance. The CPU cycles required to read a block from the RAM disk are much higher than reading from a DMA disk controller, and it still goes through the usual buffering and RAM cache that a real disk block goes through. The result is that fewer CPU cycles are available to users when the RAM disk is in use when compared to the same I/O load from a real disk. So, if you have a busy system (there is always a computable process ready to jump in when another is waiting for a disk I/O), you will probably do better overall by sticking with normal VMS disk caching than by giving up memory to a RAM disk. Capt Jon L. Spear AFWL/NTC, KAFB, NM 87117-6008 Disclaimer: This information is provided for comparison purposes only. Your actual mileage may be different. ------