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Text File | 1992-11-30 | 22.5 KB | 567 lines

COMBI-Disk - RAM disk & disk cache Preface. -------- - Why don't You use disk cache? - I'd like, but memory constrains prevent me from using it: I need more memory for RAM disk. ----- - Why don't You use RAM disk? - I'd like, but memory constrains prevent me from using it: I need more memory for disk cache. ----- - Why don't You use RAM disk or disk cache? - I'd like, but some of my applications require free extended memory. If one of these answers is Yours then COMBI-Disk is for You! You may hit THREE targets with a single shot - installing COMBI-Disk You get a RAM disk and a Disk-Cache and free XMS memory at the same time in the SAME area of extended memory! When You install COMBI-Disk You specify amount of extended memory for it and You get a RAM disk of the specified size and a Disk-Cache of the same size. You may also specify amount of memory which should be released if some program requires it. Then when You work with Your PC, You enjoy COMBI's disk cache which is not worse than others (I hope it is better). Suppose now that You start a program which needs a disk buffer for temporary storage and tell it to use RAM disk. Then the program may use the whole amount of the RAM disk's space (though contracting the size of cache). When it terminates and deletes temporary files You get back your cache buffer! If a program requests XMS memory COMBI-disk may loan some of its memory to the program (if it has the requested amount free of RAM disk data). When the program releases the memory COMBI-disk reallocates it back. Applications. ------------ Some programs (e.g. compilers, word-processors etc.) need a buffer for temporary storage, and if the storage is RAM disk then their performance may be increased few times compared with the case of usage of hard disk instead. That's why You may sometimes need a RAM disk. But if You use standard RAM disk (Microsoft (C) RAMDRIVE.SYS or IBM (C) VDISK.SYS or any other) it often comes out that it stays empty most of the time though consuming Your extended (expanded) memory. That's why You may wish to give up using RAM disk or make it less in order to have more memory for disk cache which is always useful. Moreover, some of programs can take advantage of XMS memory if it is available. That's why You may wish to give up using disk cache (though some of caches support memory reallocation without reinstallation). Don't get disappointed! COMBI-Disk is a nice solution of this problem! It uses a little more memory for RAM disk than is needed to keep all files written into it while all the remaining memory is used for cache. You need not bother to make this memory larger - just WRITE Your file(s) into RAM disk, all the rest it does itself! You need not bother as well to contract RAM disk's size and increase cache size - just DELETE files from RAM disk and all the released memory will be used for cache! You need not bother to reconfigure Your system when You need some free XMS memory - COMBI-disk takes care of that itself (however, if You forgot to specify amount of memory COMBI-disk would release, You have to run COMBI control program to tell COMBI-disk that You need certain amount of free XMS memory). System requirements. ------------------- 1. 80x86 based machine with extended memory. 2. DOS 3.30+. 3. Extended memory manager which supports XMS 2.0 specifications which supports "reallocate XMS" function (Microsoft (C) HIMEM.SYS ver 2.77+ or Quarterdeck (C) QEMM.SYS will do, as well as most others). General features. ---------------- - COMBI-disk may use up to 16 Mbytes of extended (XMS) memory. - Up to 8 physical hard disks are supported. - Starting from version 1.00 background write caching is supported. - Automatic reallocation of XMS memory. - Variable size of cache block (memory allocation unit) - from 1 to 8 disk sectors (512 bytes each). - IOCtl interface to control program. - HMA may be used for COMBI-disk data tables (even when MS-DOS 5.0 is loaded into HMA and under DR-DOS 6.0 as well). Installation. ------------ Warning! It is recommended to make backup of hard disk before installation of COMBI-disk (as well as any other disk cache program). COMBI-Disk installation process is quite straightforward, although it requires some tweaking with the contents of your CONFIG.SYS file. Copy COMBI.SYS into Your hard-disk and insert the following line into Your CONFIG.SYS file DEVICE=[drive:][path]COMBI.SYS [<parameters>] The proper place in CONFIG.SYS would be after all memory managers, after disk managers and if possible before disk write-protection programs (otherwise You should not turn on write caching). The <parameters> are all optional and include: [<buff_size> [<rls_size>]] [/V [<RAMd_parms>]] [/C [<cache_parms]] [/H] [/Q] <buff_size> - the amount of XMS memory (Kbytes) You want to use for COMBI-Disk. Minimum is 128K, maximum is about 14000K. If it is omitted then all available memory is default. There is no harm if You specify more memory than really is available - then COMBI-disk uses all available memory. <rls_size> - maximum number of XMS memory (Kbytes) COMBI-disk should release when it is requested. Default is 0. Note, if You want to specify this number You should also specify <buff_size>. /V - means that RAM disk parameters follow. <RAMd_parms> - RAM disk parameters may be the following: F:<disk_size>- specifies formatted size of RAM disk. By default COMBI creates RAM disk of the size (<buff_size> - <rls_size> - - <min_cache>) Kbytes, so that there would never arise problem that there is not enough free XMS memory to allocate for RAM disk. But You may (and I recommend You) specify larger size: up to (<buff_size> - <min_cache>) - that gives You maximum flexibility though sometimes may cause errors if the same program that borrowed XMS from COMBI tries to write a lot to RAM disk. R:<root_num> - number of entries in root directory of RAM disk. Default is 64. If You encounter DOS error "can't create file..." when number of file in root directory is 63 (plus one for volume label) then try specifying, say, R:128. S:<sect_size>- sector size for RAM disk - 256 or 512 bytes, default is 512 bytes. Using 256 bytes sectors may sometimes save some space on RAM disk but this is effective only if RAM disk size is less than 1 Mbyte. N - tells RAM disk not to return 'sector not found' error (see also below). This setting may be always changed by control program. /C - means that cache parameters follow. <cache_parms>- cache parameters may be the following: M:<min_cache>- specifies minimum cache size (Kbytes). This reduces size of RAM disk but guarantees that specified amount of memory will be always allocated to cache. Default is 0. U:<block_sec>- number of sectors per cache block (from 1 to 8). Using smaller blocks may result in more effective usage of memory (if You have not much of it) but leads to slower operation for large read/write transfers. Default is 8. O - tells COMBI-disk to turn OFF disk cache after installation. Cache may be turned ON at any time by control program. This may be useful for testing period if You have some problems. B - enable background disk writes. By default background writes are set off on installation. May be changed at any time by control program. I - forces COMBI's disk cache to start background writing immediately. By default background writing starts within 18 timer ticks (approx. 1 sec.) after last access to hard disk. This is in effect only when background writing is enabled. I admit that sometimes it may be more safe to start writing immediately rather than wait a second, but as a rule that slows down cache performance, especially for large transfers. /H - tells COMBI-disk to use HMA for data tables. /Q - tells COMBI-disk not to display installation parameters. In short, recommended installation parameters for best performance are: DEVICE=<drive>:<path>COMBI.SYS 16000 16000 /V F:16000 /C B /H In this case COMBI allocates all available XMS memory but will release almost all when it is requested, RAM disk is created of maximum size and write caching is enabled. (You may use other numbers instead of 16000 if You have less than 16 Mbytes of XMS or don't want to spend all XMS for COMBI.) Note: Minus ('-') may be used everywhere in command line instead of slash ('/'), and equal sign ('=') instead of colon (':'). Case of the letters is insignificant. Spaces are required only after COMBI.SYS name and between two adjacent numbers. Installation messages. --------------------- COMBI-Disk: RAM disk & disk cache Copyright (C) 1991, 1992 by Vadim V. Vlasov, Moscow, Russia, Version 1.10 - This banner always appears and tells You that COMBI-disk is being installed. ERROR: Incorrect DOS version! - DOS version must be above or equal to 3.30 and below 6.00. ERROR: Invalid parameter! - An invalid parameter appears in command line or some parameter is specified in improper place. ERROR: Extended Memory Manager not present! - COMBI-Disk needs XMM driver. Check that Your XMM driver is installed before COMBI-Disk. ERROR: No extended memory available! - All Your extended memory is used by some other programs or less than 128K is available. ERROR: Can't allocate extended memory! - An error encountered when COMBI-Disk tried to allocate extended memory. ERROR: Not enough memory! - Not enough memory for COMBI-disk's code and data. This is almost impossible. ERROR: No hard drives on system(?!) - COMBI-disk can't determine presence of hard disk(s) and its (their) parameter(s). WARNING: Inconsistent parameters. - Some of numeric parameters conflict with each other. As a rule this is not fatal - some of the numbers will be adjusted. WARNING: Can't hook XMS driver entry chain. - COMBI-disk won't intercept XMS (re)allocation calls and hence automatic reallocation of COMBI's memory is disabled. However, You may change amount of used XMS memory by control program. WARNING: Not enough HMA for data tables or HMA not available. - COMBI-disk will use more low memory for its data tables. (For 3 Mbytes buffer it is about 10K) If "ERROR:..." message is displayed COMBI-disk aborts installation. If the installation is successful a table appears (if it is not disabled by /Q switch) which summarizes installation options and announces how much memory is used by COMBI-disk. Note. Some of numeric parameters specified in command line may be adjusted by COMBI-disk. Testing. ------- A simple test program CMBTEST.COM is supplied with the package. It writes randomly to few files, deletes some of them etc. Its objective is to convince You that memory allocation strategy used by COMBI-disk is reliable. It may also be used to test write caching reliability. Usage: CMBTEST <dirname> [<options>] where <dirname> is name of directory (or drive) where CMBTEST will write the files - it may be a directory on a hard drive or COMBI's RAM disk. <options> may be used if You want to run multiple test series. (For more details see the source code CMBTEST.C) I suggest You to run CMBTEST <COMBI's_RAM_drive_letter>: and then CMBTEST <some_temporary_directory_on_hard_disk> and compare the resulted files: COMP <path1>*.* <path2> (<path1(2)> - pathnames of target directories). If all the "files compare O'K" then there is no error and You may delete the files or repeat the test with other options. Note: options must be the same for both runs otherwise the files will be different. You may also change the program if You have any new ideas how to improve the test. Control of operation. -------------------- A control program COMBI.COM is supplied with the package. It allows You to change cache or RAM disk options or change memory setting without reconfiguring and rebooting. It also displays some statistic information which may be helpful: current options, number of read/write accesses to hard/RAM disk etc. Usage: COMBI [+/-<mem_change] [<options>...] where <mem_change> - amount of memory (Kbytes) to add to or release from COMBI-disk. If memory can't be reallocated by specified amount COMBI will report that. <options> - a sequence of any of letters 'i', 'o', 'b', 'z', 'f', 'r', 'n' which may be separated by spaces and/or followed by '-' which reverses the meaning of the option. Case of the letters is insignificant. i - turn off delayed writing (write immediately) ('i-' turns delayed writing on), o - turn cache on ('o-' - turn off), b - enable background writing ('b-' - disable), z - 'freeze' cache - after freezing the sectors which are already in cache remain there (are not purged) while no new sectors are copied to cache. This may be useful e.g. if You have small cache and want to keep there only FAT and directories, then You might run "CHKDSK" (which reads the whole FAT and all the directories) and then "COMBI z". 'z-' returns cache to normal operation. f - fix memory settings - this disables automatic reallocation of XMS memory to other programs. n - tells RAM disk not to return 'sector not found' error. r - resets all statistic counters (there is no 'r-' option). "COMBI ?" displays quick help on parameters usage. Source code COMBI.C and header file IOCTL.H are provided if You wish to implement some control over COMBI-disk into Your applications Compatibility. ------------- COMBI-disk is compatible with: - MS-DOS versions 3.30 - 5.00 (if it were not it would be useless); - DR-DOS version 6.00 (version 5.00 was not tested); - Borland's Turbo-debugger TD386 (TD386 uses XMS memory released by COMBI-disk); - MS-WINDOWS; - DJGPP (GNU C++ compiler for DOS and GO32 DOS extender by DJDelorie), however LD (DJGPP linker) often runs into "Sector not found" error if some of object files are on RAM disk, usage of "N" installation option or "COMBI n" solves the problem; - many other programs. COMBI-disk is incompatible with: - Maybe some multitasking programs (please report me about any incompatibilities). Possible errors. --------------- Sector not found - You tried to read a sector which does not contain any valid data (You haven't written into it yet or have already deleted the file that occupied this sector). This never happens with the majority of programs. However, for some programs this occurs regularly. It is recommended to reply 'Ignore' to the 'Retry, Ignore, Fail?' DOS prompt. If You are sure that this causes no errors You may specify option 'N' as one of installation parameters (or run "COMBI n"). In this case the 'not found' sectors are also not read, but error status is not returned by COMBI-disk. Warning! Once a file is deleted from RAM disk, it might not be correctly unerased by any means. It's data is lost immediately. Data error writing drive <RAM_disk> - this may happen when some XMS memory has been loaned to a program and that program also tries to write some files to RAM disk which has not enough memory for that. Suggested action - specify less amount of memory which COMBI-disk should release for other programs or configure the program to use other drive for temporary files. The same problem may arise if a program which used XMS memory terminated (or has been aborted) but not released memory. In this case COMBI-disk can't reallocate XMS memory back to the full size. It continues working but won't use the full buffer size for cache or RAM disk data. Other errors indicate that either COMBI-Disk internal data tables are corrupt (e.g. overwritten by other program) or error in XMM driver encountered. Some hints. ---------- "TEMP" environment variable is used by MS-DOS as a directory for temporary files, in particular when COMMAND.COM creates pipes (e.g. "dir | sort | more" etc.). "TMP" environment variable is used by many programs (e.g. Microsoft compilers) as a directory for temporary files. So, setting TEMP and TMP in AUTOEXEC.BAT to point to Your RAM disk may improve Your system performance. Many other programs also can take advantage of RAM disk - see their manuals and configure them. Using write caching is not very dangerous as it might seem. In fact, when COMBI-disk is configured for background writing it often takes less time to finish writing to hard disk than without write caching. Moreover, while data is being written to disk You program continues working and that saves You a lot of processor time. Enabling delayed writing as a rule decreases number of hard disk accesses and hard disk head motions. However, if You start a program that hooks INT 08 (timer) and does not pass control to former INT 08 handlers (some games often do so) it would be better if You disable delayed writes ("COMBI i") before starting such a program and enable it later ("COMBI i-"). Freezing cache ("COMBI z") when it contains certain data may be useful if COMBI-disk's buffer size is relatively small. E.g. Freezing cache after "CHKDSK" results in faster search for a file or directory change, freezing cache after run of some program (whose size is less than cache size) results in faster loading of that program on future runs (while other programs operate as without cache). The name of the game. -------------------- The name "COMBI" originates from "COMBInation" of such incompatible (maybe even contradicting) at the first sight programs: RAM disk and disk cache. History information. ------------------- Version 1.10 (01 Dec 1992): Few bugs of version 1.00 were fixed. These include: - "Not enough memory" error under DOS other than MS v.5.00; - Very poor performance (worse than without cache) if VERIFY is set ON. Now COMBI may use HMA under DR-DOS as well. Performance of cache improved. Write delay time increased from 5 to 18 clock ticks (1 sec). Added Ctrl-Alt-Del handling to flush cache before reboot. COMBI control program renamed from "CMBCTL" (which was hardly typeable and hardly rememberable) to "COMBI", ANSI sequences are used to provide color output. Version 1.00 (08 Aug 1992): A lot of new features added compared to previous versions: write caching, reallocation of XMS memory, IOCtl interface to control operation of COMBI-disk etc. Most of the code has been completely rewritten. However, the main idea of dynamical memory reallocation between RAM disk and disk cache remained the same. Version 0.31 (15 Feb 1992): Few minor bugs of version 0.30 fixed. No other serious changes. Version 0.30 (08 Nov 1991): Performance of delete from RAM disk operations increased compared to previous versions. For certain configuration parameters (e.g. 320 /v 128 256) COMBI-Disk created FAT larger than really needed. However, it was O'K for DOS 5.0 but led to errors with DOS 3.30. - Now it is fixed. Version 0.20 (28 Oct 1991): A bug has been discovered in version 0.10: RAM disk failed after an attempt to write into boot sector and one or more sectors of FAT. - Now it is fixed. DOS 4.0+ CHKDSK did not work with version 0.10 due to simplified format of boot sector of RAM disk. - This is now corrected for MS-DOS 5.0 but some DOS versions need a certain text be written into boot sector (e.g. for IBM-DOS 4.0 it is "RDV 1.20" at offset 3 of boot sector). If You are aware what You are doing, You may correct this problem for Your DOS. Version 0.10 (13 Aug 1991): The very first beta version of COMBI-Disk was version 0.01 (24 Jun 1991). In this version (0.10) two minor bugs have been fixed: A. COMBI-Disk v.0.01 refused to work under DOS 3.30 - not just it couldn't but only refused. B. Device return codes were corrected. No any serious bugs were discovered yet. Future. ------ Here are some of my ideas about future developement of COMBI: - Caching of floppy disks; - Special version for 80386 processor (probably, usage of 80386 instructions may increase performance); - Reallocation of XMS memory allocated to other programs is not currently supported (some of programs allocate XMS and then reallocate it to larger size) - that will be certanly done; - As regards usage of EMS instead of XMS, I'm not sure that it would be an advantage. However, if there is enough interest in that I'll implement EMS support; - Further improvement of performance. ---------------- If You have any questions, comments or find out any problems with COMBI-disk usage please contact: Vadim V. Vlasov, Inst. for Nuclear Research of Russian Acad. Sci., 60th October Anniversary prospect, 7a, 117312, Moscow, Russia. phone: 7-095-133-6533 Internet: vvlasov@inucres.msk.su