On the "HPFS" and "FAT" pages of the object "OS/2 Kernel" you may change the CONFIG.SYS settings which influence the administration of these two file systems on your system.

For an introductory description of file-system caches, please read the respective chapter in the "Introduction" of the XFolder Online Reference.

If the information on this page regarding the different CONFIG.SYS settings is not sufficient for you, you'll find additional explanations in the respective chapters of the OS/2 Online Reference.

Press "Apply" to have the changes you've made written to the CONFIG.SYS file. This will only change the CONFIG.SYS lines which correspond to the settings on this page. The lines corresponding to the other pages in the "OS/2 Kernel" object will not be changed. This button is only active if you have made any changes to the settings on this page. Please note that you will have to restart the computer to let the changes take effect. A WPS restart does not suffice.

Press "Optimize" to have XFolder propose you new settings according to your system characteristics. CONFIG.SYS will only be changed after you press "Apply" also.

Press "Default" to have the OS/2 default settings displayed on the notebook page. CONFIG.SYS will only be changed after you press "Apply" also.

On the "HPFS" page you will find a setting called "HPFS installed". If you do not have any HPFS drives, you can save several hundred KB of memory by deactivating this setting, which will not load the driver HPFS.IFS at system startup. If XFolder has detected HPFS drives on your system, this setting is deactivated to prevent accidents.

On both settings pages you'll find the following settings:

- Cache size determines how much KB of main memory will be reserved for the cache of the respective file system. This corresponds to the CONFIG.SYS parameter /CACHE:xxx in the IFS=?:\OS2\HPFS.IFS command for HPFS drives and DISKCACHE=xxx for FAT drives.

  According to IBM's documentation, the maximum cache size for HPFS drives is 2048 KB; for FAT drives, it's supposed to be 14440 KB.

  Please keep in mind that memory you reserve for file-system caches is no longer available for other purposes. If you reserve too much cache memory, this will have a negative impact on your system performance, because OS/2 will spend more time on your swap file. As a result, you should reflect a bit on what settings you specify here.

  In general, the more memory you have on your system, the more memory you should reserve for the caches. You should also take in account which file systems you use more frequently: for example, if you mainly use HPFS drives, it's a waste to reserve much memory for FAT caches, and vice versa. On my system with 32 MB RAM I have reserved 2048 KB for HPFS and 1024 KB for FAT. If you only have 16 MB RAM or less, you shouldn't reserve more than 1024 KB cache for both file systems altogether.

  For both file systems you may request that OS/2 automatically determine the cache sizes. In most cases, this will then result in about 10% of the installed memory, but I don't recommend this setting.

- The setting "Only save files smaller than" determines (in KB) the maximum size of objects that will be saved in the caches. This corresponds to the CONFIG.SYS parameter /CRECL:xxx in the IFS=?:\OS2\HPFS.IFS command for HPFS drives and the second parameter in DISKCACHE=xxx for FAT drives. This setting prevents large files which are usually only loaded once from filling up the whole cache. However, I think that the default value of 4 KB is way too low. On my system, I have set these values for both file systems to 32 KB. (XFolder will automatically convert the FAT value to the sector size that is expected in CONFIG.SYS.)
- The "Autocheck" entry field corresponds to the CONFIG.SYS parameter /AUTOCHECK:xxx in the IFS=?:\OS2\HPFS.IFS command for HPFS drives and the /AC:xxx parameter in DISKCACHE=xxx for FAT drives. Here you can determine for which drives OS/2 will automatically perform a CHKDSK at system startup.

  Simply enter the respective drive letters here (without the trailing ":"). OS/2 will check each drive that you specify here at system startup if you have not shut down your system properly. If you specify a plus sign ("+") before a drive letter here, that drive will always be checked, which is not recommendable.

  Example: If you enter "C+DE", drive D: will always be checked, while C: and E: only if needed.

  For HPFS drives, the auto-check is absolutely neccessary. You should enter all your HPFS drives here because OS/2 will print error messages at startup otherwise. This applies especially to your boot drive, or OS/2 will refuse to boot altogether if you forgot to shut down. For FAT drives, auto-check is not obligatory though.

  Press the "Propose" button to have all the HPFS or FAT drives of your system added to the entry field.

- The "Lazy write" setting determines whether OS/2 is allowed to hold data which is to be written to disk in the caches before it's actually written. This will improve your system's performance also, but increases the danger of data loss if you do not shut down your system properly or press Ctrl+Alt+Del, but simply switch off your system, because data in the caches gets lost then. You should still have lazy writing enabled.

  This setting corresponds to the parameter /LAZY:x in the command RUN=?:\OS2\CACHE.EXE for HPFS drives and the parameter LW in the command DISKCACHE for FAT drives. Per default, lazy writing is enabled.

For HPFS drives you may influence lazy writing in a more detailed way. The following values all belong to the line RUN=?:\OS2\CACHE.EXE, which can optionally be written into CONFIG.SYS (and will always be written if you let XFolder modify your CONFIG.SYS).

- The "Maximum delay" setting corresponds to the /MAXAGE:xxx parameter and determines the maximum time that data may be held back in the caches before it will be queued for being written to disk. The default value is 5.000 milliseconds; several sources recommend to raise this to more than 7.000 milliseconds. Since increasing this value also increases the risk of data loss, you should only set this value much higher if you never experience any system crashes. Note that if you shut down your system or press Ctrl+Alt+Del, all the cache buffers are written to disk, so there's no danger here. "System crashes" in this context mean complete system halts or power failures which will cause a CHKDSK at the next bootup.
- The "Cache idle time" and "Drive idle time" settings together determine the write delay in relation to drive activity. These settings correspond to the /BUFFERIDLE:xxx and /DISKIDLE:xxx parameters. There seems to be much confusion about these settings, and the explanation in the OS/2 Command Reference really leaves you even more confused. The best explanation I've found for this is from IBM in the Toolkit documentation:

  When no disk request has been made for the time specified with "Drive idle time", i.e. a disk has not been accessed for that time, all cache blocks that have not been modified for the time specified with "Cache idle time" will we written to disk. As a result, raising these two numbers will increase the chance that redundant disk accesses can be avoided.

  Some sources recommend raising both of these values to as much as 60.000 milliseconds; however, IBM also recommends that the "Disk idle time" value be set greater than the "Cache idle time" value, which, in my view, makes sense, because otherwise some cache areas might not be written at all. The default values for these are 1000 and 500 milliseconds, respectively.