Dennis Snelgrove said:
I'm running Vista Home Premium 64 bit. I'd like to set up a RAMdisk or
a virtual drive. I've looked at Daemon Tools, but it seems that what
I've got in mind is not what a virtual drive is these days. I used one
about 10 years ago which was simply a RAMdisk; it used memory to
emulate a floppy disk. It allowed me to write and read files like a
floppy but with the speed of memory access. Daemon wants to set up CD/
DVD images, which is much more than I need or want. Is it possible to
use a virtual drive as a temporary drive where I don't care to keep
the contents when I'm done? Alternately, how do I set up Daemon with a
Hi Dennis,
The concept of RAM Drive is not really useful on Windows NT (including under
the "NT" label, NT 4.0, Windows 2000, XO, Server 2003 and Vista).
In these versions of Windows, the operating system will automatically use
any unused physical memory as a File System Cache. Reading and writing of
files will take advantage of caching, and clever "write-through" and
"lazy-write" mechanisms, to speed up disk /IO.
By creating a RAM Disk, you are taking memory away from the file system
cache, in order to create a fast drive for files - it's "robbing Peter, to
pay Paul".
People sometimes post here to ask "Why is Vista using all my memory when the
system is sitting idle? Is it a memory hog?". In fact the answer is: No;
Vista is pre-emptively using spare memory for many useful purposes
including, especially, System Cache.
There was a RAM Disk included as a sample in the Windows 2000 Device Driver
Development Kit (DDK). This sample wa intnded more as a tutorial aid and
curiosity, rather than as an industrial-strength data processing tool. But
some people who really want a RAM Drive on Windows have used it. See:
http://support.microsoft.com/default.aspx?scid=kb;en-us;257405
As far as I know this has not been tested on Vista by Microsoft, and not
supported - but it might work.
For an overview of the Windows Cache Manager, see this article:
http://www.microsoft.com/technet/prodtechnol/windows2000serv/maintain/optimize/wperfch7.mspx
It refers to Windows 2000 but the same broad mechanism applies to Vista as
well.
To get a feel for the sophisticated smarts which go into the Windows Cache
Manager, watch these 2 interviews with Molly Brown, the Microsoft developer
who has done a lot of the recent cache work in Vista:
http://channel9.msdn.com/ShowPost.aspx?PostID=59936#59936
http://channel9.msdn.com/ShowPost.aspx?PostID=60627#60627
It's possible there are a few limited scenarios in which a RAM disk would
provide a worthwhile I/O performance boost. But it's unlikely that *overall*
system performance will improve significantly; and more likely that it will
decline, due to less available RAM.
Back in MS-DOS days, a RAM Disk was useful because -
- many machines had XMS memory which could not be used by the operating
system anyway; and
- disk I/O to ST-506, ESDI, etc hard disks was so very painfully slow, that
any performance boost was worthwhile.
Unlike DOS, Windows *can* use all the memory on the box. Obviously modern
hard disks are still far slower than memory speeds; but they're nowhere like
as bad as they used to be. If you have an app which does heavy disk I/O and
you'd like to speed it up, you'd be better off trying a strategy like:
- buy a 10,000 rpm SATA Drive (they're fast!)
- use a SCSI drive
- set up a RAID array
2 new performance features in Vista are ReadyBoost and ReadyDrive:
http://www.microsoft.com/windows/products/windowsvista/features/details/performance.mspx
These are somewhat similar to the idea of a RAM Drive, but not quite the
same - they increase overall system memory, by means of Flash memory on a
USB drive.
Daemon Tools is a great tool, I run it all the time; but yes: it's oriented
towards CD-ROMs and DVDs, nothing else.
Hope this helps,
