Post
by code65536 » Sat Jul 21, 2007 1:14 pm
The other thing that I don't quite get is how a cache on a RAM disk will speed up browsing for a user with a low bandwidth connection. For that user, the speed is limited by the bandwidth, and it will be so limited by the bandwidth that any speedup from a memory cache would be negligible at best. In fact, because the memory cache is volatile and thus data cannot be cached between boots, this would actually reduce performance. The only instance where a cache on a RAM disk would improve performance is a case where a user has very slow disk access, in which case, if memory usage could be favored over disk usage (though keeping in mind that reducing the memory available will increase the likelihood of disk paging), in which case, this could be accomplished with Firefox by killing the disk cache and boosting the memory cache (no need for a RAM disk). A RAM disk would thus be needed only for browsers with no memory cache or a memory cache whose size cannot be configured (i.e., IE). But with modern-ish computers (basically, any box from, say, 1999-2000 or beyond), disks should not be that slow that a performance gain would be observed with a RAM disk. And if your computer is new enough that it has a RAM to spare for a RAM disk, then it probably has a sufficiently speedy disk.
In other words, if a RAM disk is improving web browsing performance, then either 1) you've got a slow disk (once again, this would be independent of connection speeds and the slowness would be observed regardless of speed and in activities that are done apart from transmission) or 2) it's a placebo effect. It's a simple matter of cache speeds being totally unrelated to the amount of bandwidth that could be carried over the voice frequencies of a POTS.
The only real use I've had for a RAM disk is when HDD access is not possible or not desirable (e.g., booting from a CD ROM and wanting to limit all your activity to a RAM disk because either there is no HDD or you want to limit the "footprint" of what you're doing so that you don't touch the HDD).
