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- Path: sparky!uunet!utcsri!eecg.toronto.edu!lemieux
- Newsgroups: comp.os.os2.misc
- From: lemieux@eecg.toronto.edu (Guy Gerard Lemieux)
- Subject: Re: os/2 ram drive
- Message-ID: <1992Jul28.215920.24741@jarvis.csri.toronto.edu>
- References: <1992Jul27.1480.23146@dosgate> <92210.133859BRYAN@wvnvm.wvnet.edu> <Bs48Dq.4F8@news.cso.uiuc.edu>
- Distribution: comp
- Date: 29 Jul 92 01:59:20 GMT
- Lines: 41
-
- tamu@uxh.cso.uiuc.edu (Todd Henderson) writes:
-
- >Jerry Bryan <BRYAN@wvnvm.wvnet.edu> writes:
-
-
- >>6. A RAM disk can totally eliminate disk I/O if you have enough memory.
- >> Disk caching does not eliminate all I/O because all writes happen
- >> eventually, even with lazy write.
-
- >I will not claim to be to knowlegdable about ram disk, io, etc., but it
- >seems to me, you are saying:
- >1. Make a ram disk.
- >2. Put your swap there. This gives no disk i/o if you have enough memory.
- >Am I missing something here?
-
- Yes, you are. Putting your swap in the RAM disk makes zero sense. Rather,
- put frequently accessed files in RAM.
-
- Simple example: when compiling a small C program, most of the time is
- spent reading and processing the OS/2 header files. If I put the header
- files into a RAM disk, the access time is zilch. With disk caching, I
- take a chance that my cache is not large enough AND that because I am
- multitasking, my header files get flushed from the cache.
-
- Speaking of lazy writes: when I am doing heavy writing and reading
- to a file, chances are it will be cached. If I stop writing to the file,
- the lazy cache will timeout and then write the changes to the disk. If
- this file is only a "temporary file", it need not be written to disk because
- it will only be deleted soon anyways. Thus, the disk access is wasted.
-
- When you know how much space you need, and how frequently you want the
- information, a RAM disk makes sense.
-
- Personally, I would like a DYNAMIC RAM disk. As I copy files into it,
- it grows in size (until I'm out of physical(virtual?) memory). This way
- I never have to worry about making a SIZE setting in my CONFIG.SYS and
- rebooting.
-
- The alternative is to give us memory mapped files ala BSD.
-
-
-