Swap File Optimizations?

fastswap asks: "I've got a pretty standard computer with reasonably fast drives. I've got an old 2GB-but-fast drive, and a spare channel on the motherboard. Does it make sense to install the 2GB drive on its own controller and use it for a dedicated, fixed swap file? I figure if the computer's using the swap file, then in the current setup with the swap file on the primary controller, then it's contributing to hard drive thrash exactly when one doesn't want it to (i.e. when the machine needs the swap file). If it is better to have a dedicated swap file on its own controller, is the same true for other operating systems with similar approaches to virtual memory? Since drive space is so cheap now, should the swap file be fixed size anyway rather than letting Windows suddenly get the urge to resize the thing?"

Comments

Yes, seperate drive and fixed size

[viware]

My experience has always been to give windows a fixed page file, at twice the RAM size (ie. 512MB RAM so 1024MB page file). Further, a separate physical drive is the best scenario, or second best is a separate partition.

It is important to note that WindowsXP will use the page file whether you've got plenty of RAM or not.

The HD sounds like a good idea

[PurpleFloyd]

As far as using the HD goes, it sounds like a good idea, albiet with some conditions:

• If you're planning on spending any money on this, it would be better off going towards more RAM.
• If the drive isn't as fast as your primary HD, it may not be as good a deal as you might think. Remember that the non-DMA access modes used by older IDE drives, can eat up your CPU and thus any performance gain. Of course, this isn't an issue with SCSI if that's what you're using.
• If you use an app that has its own scratchpad requirements, you might want to put that on the drive rather than your Windows swapfile. Photoshop comes to mind immediately as an example of where this would be a good thing; it might also be good for dumping processed video onto (although if you're doing major video work, you should have a fast, preferably RAID-0, scratchspace, along with more reliable storage).

As far as a fixed-size swapfile, it should help some in Windows; when you defrag, it will help to keep your swapfile coherent as much as possible. Of course, if the swapfile is the only thing on the drive, it won't matter too much. If you do go for a fixed size file, make sure to make it larger than you ever think you'll need - it sucks to run out of memory when you're doing a lengthy, complex operation. One rule of thumb (not as valid these days) is to set your swap to 2x your physical memory. Another, which I use, is to simply take the most memory you'll ever think you'll use and then add a 50% safety factor. Remember to resize this if you ever start working with really large stuff - high-res video, 3000 x 3000 pixel Photoshop images, etc.

Finally, remember that idealy, you never want to hit swap at all. If you're experiencing problems with thrashing, you should probably either pare down your system (do you really need to run that IM program all the time? all those systray utilities you never use?) or simply bite the bullet and get more RAM. Even the fastest hard drive can't touch RAM for speed, and seeing your system hit the pagefile for routine tasks means it's time to put a new stick of RAM into the beast.

Re:swapping?

[ColaMan]

Close Word and you'll probably gain 100MB :-)
No, seriously.
I don't know what the hell kinda easter egg's in Word - I know Excel had a flight sim , maybe Word's got a 5 minute video of BillG rolling naked in a pile of money and whores.

One Word Answer: No

[silverfuck]

Okay, so this is too late for all but the most sad of slashdotters to read it, but here goes:

If the drive is 2GB, then don't be so sure that it is fast - it may have been when it was bought, but that was 6 or so years ago at least. I would be very suprised indeed to see more than 4-5MB/s sustained read and 2-3 write; there have been a lot of advances in the last few years.

My current setup (1GB physical RAM) has 2GB set aside for each of Win2k and Linux in seperate partitions right in the middle (this will speed up average access times as the heads will have the least far to travel on average from any random point over the platters) of the raid array (and hench middle of both disks, as it is RAID-0), which I know to be fast - benchmarking has pegged it at greater than 110MB/s sustained. Windows will hit the swapfile no matter what (just try setting the swap to 0, even on a well-heeled system, and watch it complain at bootup/logon), so it gets 512MB to play with just at bootup and can go all the way to the end of it's swap partition if it wants. Linux, well, that's another story (currently support for the raid array is patchy, so not running linux - the partitions are still there, though, waiting for filsystems!), but as everybody knows, linux is very aggressive about swapping stuff out and using physical RAM as a disk cache, so again I expect it to hit the swapfile after a few days (hours?) running, but be perfectly happy with 2GB.