dhw@itivax.iti.org (David H. West) (11/25/89)
Has anyone seen an MSDOS ramdisk which, when full, overflows uncomplainingly onto real disk? That way, when ram is scarce, one could have the speed advantages of ramdisk much of the time by allocating to ramdisk what little ram one can spare, without risking the fatal errors otherwise resulting from ramdisk overflow. I have in mind the use of ramdisk for a /tmp directory, for which the frequency distribution of space-required vs. occasions-of-use is very skewed. This isn't trivial to write, because in some circumstances every file on the ramdisk might need to be continued on real disk, and so might the root directory (maybe avoid the latter problem by keeping the ramdisk cd'ed to a subdirectory?). Freeware or shareware preferred; I have ftp. -David West dhw@itivax.iti.org
walter@hpsad.HP.COM (Walter Coole) (11/30/89)
You could get many of the features you mention by using a cacheing program, of
which there are many available; my favorite is PC-KWIK, available shareware
from a variety of sources.
The main limitation of caches is that since DOS can't run a synching
process, writes can't be cached. Typically one reads far more than one writes,
so this isn't a major disadvantage.
I tested PC-KWIK in a disk search, and found ~12x performance improvement
with ~100k devoted to cacheing.dhw@itivax.iti.org (David H. West) (12/01/89)
In article <720017@hpsad.HP.COM> walter@hpsad.HP.COM (Walter Coole) writes: |You could get many of the features you mention by using a cacheing program, of |[...] The main limitation of caches is that since DOS can't run a synching |process, writes can't be cached. Typically one reads far more than one writes, |so this isn't a major disadvantage. [mentions 12X performance improvement in upspecified application] For my intended application (a /tmp directory), files are typically created, read once, then immediately deleted. This means that a cache can save no more than half the disk accesses unless it delays writing long enough to see the delete. I don't know whether lazy writing is common, but I suspect not. I'll probably end up using a cache anyway, since - one came free with my computer (but it uses immediate write-through) - no-one has pointed me to a soft-overflow ramdisk - I don't have time to hack on ramdisk code. Thanks to all who responded. -David dhw@itivax.iti.org