Disk Caching Programs  by Dave Hooton   36 -+- 36 -+- 36 -+- 36 -+- 36 -+- 36 -+- 36 -+- 36 -+- 36 -+- 36  The main purpose of the exercise was to test the usefulness of disk caching programs in improving input/output (I/O) to either hard disks or floppy disks. A cache is an intelligent buffer. You might be familiar with buffers via the AddBuffers command, knowing that the more buffers you add, the better the performance of your drive. You typically have 20 buffers on a floppy and 30 buffers on a hard drive. This equates to about 10k and 15k respectively of memory, usually chip memory. A cache is much larger, typically 512k! And it applies to a device e.g. you will have one cache for HD0: and HD1:, whereas each drive will have 30 buffers of its own. A cache can work in conjunction with buffers. A speed testing program like DiskSpeed 4.2 will show a staggering improvement in data transfer speed with any well designed cache. The downside is little or no improvement in file create speed. But, no matter how much I may respect a program like DiskSpeed, the real test is how it affects typical operations that I perform. So I ran a suite of tests involving copying and searching of data on hard drive and floppy. The results surprised me! So much that I re-ran the suite to verify their accuracy. The best I can say is that an intelligent cache is bound to take some time compared to simple buffers. I have a A1200 with 85MB Maxtor hard drive and 4MB fast RAM. Naturally enough, this uses Workbench 3.0. The programs I tested are FastCache and ClockCache, both available in the Public Domain on HotPD10a from Prime Artifax. Another PD cache program is SmartDisk (Fish 754) and then there is a commercial program called HyperCache Professional. The latter two were tested by Amiga Review in their August 1993 issue. As FastCache came in two varieties, I needed to know which was the faster for my computer and to find a cache size under 512k that was just as good. The misnamed FastCache68030 worked a bit better on my 68020 CPU, and I settled on 340k as roughly established below:- Copy WORK:Falconmission to WORK:Falcon ALL Quiet (2 sub-dirs, 109 files/1,452,300 bytes) Cache Cache Write Time Program size Delay (sec) FCache68000 512k Y 30.2 FCache68000 340k Y 30.2 FCache68030 512k Y 30.0 FCache68030 340k Y 30.0 FCache68030 340k N 19.6 None** - - 15.0 ** None usually means 30 normal buffers for a hard drive and 20 buffers for floppy drive. ================================================ The rest of the tests on my hard drive follow:- ================================================ Copy WORK:Falconmission to RAM: ALL Quiet (AmigaDOS Copy command) (2 sub-dirs, 109 files/1,452,300 bytes) Cache Cache Write Time Program size Delay (sec) FCache68030 340k Y 7.9 FCache68030 340k N 7.9 None - - 6.5 Copy RAM:Falconmission to WORK: ALL Quiet (2 sub-dirs, 109 files/1,452,300 bytes) Cache Cache Write Time Program size Delay (sec) FCache68030 340k Y 16.8 FCache68030 340k N 10.8 None - - 8.5 Copy RAM:Falconmission to WORK: (1 file/353,152 bytes) Cache Cache Write Time Program size Delay (sec) FCache68030 340k Y 1.1 FCache68030 340k N 1.4 None - - 1.2 Copy RAM:NIV.1 to WORK: (1 file/803,947 bytes) Cache Cache Write Time Program size Delay (sec) FCache68030 340k Y 9.1 FCache68030 340k N 2.2 None - - 2.1 Ami-Back scan of WORK: (Backup utility Scan) (30 sub-dirs, 700 files) Cache Cache Write Time Program size Delay (sec) FCache68030 340k Y 10.8 FCache68030 340k N 10.7 None - - 10.2 Search WORK: Siesta FILE (AmigaDOS Search command) (30 sub-dirs, 700 files) Cache Cache Write Time Program size Delay (sec) FCache68030 340k N 9.2 None - - 8.0 ======================================================== Now that my hard drive is suffering from over work, it's time to see if the floppy drive can reap any benefit. ======================================================== Copy RAM:Falconmission to DF0: (1 file/353,152 bytes) Cache Cache Write Time Program size Delay (sec) FCache68030 128k Y 26.0 FCache68030 128k N 34.5 CacheClock 128k - 33.5 None 5 buff - 35.2 None 20 buff - 32.6 Copy DF0:Falconmission to RAM: (1 file/353,152 bytes) Cache Cache Write Time Program size Delay (sec) FCache68030 128k Y 17.6 FCache68030 128k N 17.6 CacheClock 128k - 16.9*** None 5 buff - 17.8 None 20 buff - 16.7 *** the file was corrupted - not on the initial copy, but on the SUBSEQUENT copy, when it thought most of the file was in the cache and took <1 second! Goodbye CacheClock. "Find" DF0:SmallFonts1 Siesta FILE (a file finder utility) (96 sub-dirs, 258 files) Cache Cache Write Time Program size Delay (sec) CacheClock 128k - 78 FCache68030 128k Y 41 None 5 buff - 109 None 20 buff - 78 Copy files to/from floppy (e.g. Copy RAM:smallfile to DF0:) ------------------------- Cache File Cache Write Time Time Program Size size Delay Initial Subsequent FCache68030 3677 128k Y 1.5 (1.5) <0.5* None 3677 - 2.8 (1.5) + FCache68030 7744 128k Y 2.0 (1.7) <0.5* None 7744 - 3.3 (1.7) + FCache68030 44504 128k Y 2.0 (3.4) <0.5* None 44504 - 6.1 (3.1) + () time from DF0: to RAM: * same to/from DF0: + same times as Initial Summary FastCache provided best improvement on my floppy drives, which is where I have used it for an extended period. The overall benefit is that it saves a lot of drive thrashing because a reasonable number of files fit in the cache! I found 128k worked well - you may need a larger cache. I found it best to remove (Add)buffers from the floppy. One trap of updating caches that IBM PC users are well aware of, is that the update of the disk may never take place if you exit too rapidly. The only way this will happen on a multi-tasking computer like the Amiga is if you:- 1. remove the (floppy) disk too soon; or 2. reset the computer too soon. So choose the write delay interval wisely. 1 second minimum is best, with a 60 second maximum. If there is no I/O, it will update in 1 second, but it can never take more than 60 seconds to update. The only time I had problems was when using backup programs, or any program that takes over trackdisk.device e.g. SuperDuper, Ami-Back. Simply remove FastCache for such!  36 -+- 36 -+- 36 -+- 36 -+- 36 -+- 36 -+- 36 -+- 36 -+- 36 -+- 36