rdt@houxk.UUCP (R.TRAUBEN) (09/01/84)
I am interested in improving my disk sub-system from an overall systems point of view. Clearly there are a number of factors which come into play. Some are stricly mechanical, some are hardware configuration dependent, and the balance are OS software stategy dependent. I am interested in getting pointers to any books or articles which deal with these issues. Magazines and nety articles are not acceptable since the gloss/content ratio is too high. Can some one help me out? PURE MECHANICAL DISK CHARACTERISTICS are: - rotational latency, - seek time (1/3 radius travel time) HARDWARE CONFIGURATION CHARACTERISTICS are: - drive to controller data transfer rate (ST506, ST412HP, ESDI, SMD), - number of drives tied to the controller (drive bus contention & overruns), - existence semiconductor memory buffer/cacheon the controller itself, - any intelligence (policies in processor) added the controller to make dynamic track swapping, out-of-order sector transfers, out-of-chronological order disk request scheduling to mitigate seek times, prefetch behind, postfetch slightly ahead, read entire track - and defer service to any stacked prior seek request) - size of said buffers/cache - existence of main memory buffers (sys. buffer cache) outside of the controller board itself. - the width and peak transfer rate of the disk controller to main memory data transfer bus. - the peak transfer rate of the DMA controller to main memory transfer rate, - the overhead in bus arbitration policy being used by the DMA controller. (request-grant-transfer 1 word- release bus) or (request-grant- transfer entire sector then release bus). - number of busses and controllers between the drive itself and main memory (ST506, IPI, SCSI, VMEBUS, VMXBUS) - other stuff ... SOFTWARE CONFIGURATION CHARACTERISTICS are: - main memory size - page size, - page reference policy (R&M update policy in MMU) - overhead in setting up and tearing down the DMA transfer, - presence of system buffer cache, - whether 1 or 2 DMA jobs are necessary to make the blocked process runnable, (controller to user space, or controller to system buffer cache to user space) - adaptive prioritization of seek request based on length of wait interval, - other stuff ... In particular, I am interested in finding out about any published studies or unpublished personal experiences which attempted to determine which of the above get a good "return on investment" and which ones are noise. The configuration I am most interested in studying is the general purpose mini/micro market, at cost less than $100K, with 1-2 Mega bytes main store, 100 Mbyte disk with 35 ms. Send pointers to ../inhp4/houxk/rdt. Thank you, Richard Trauben AT&T Bell Labs