Talk:Virtual memory

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 Definition A concept in computer science whereby an operating system can use alternate (usually slower) data storage to impersonate real memory and run programs that ordinarily would not fit into real memory (RAM) [d] [e]

swap file distribution across disks

I don't think RAID is required to distribute a Windows paging file across two disks, only a second available disk (partition) is required, whether RAID or not.Pat Palmer 10:14, 19 January 2008 (CST)

Another odd phenomenon: if the swap file is moved entirely to a second drive, say D:, a Windows machine may well boot up faster. I think that happens because the loading of boot programs from the primary partition (C: drive) can then go on in parallel with the loading of running program parts into the page file (D: drive), so overall, everything gets ready quicker. This is the kind of crap I learned from doing a lot of system administration and spending too many hours of my life watching Windows reboot (smile). It's typically 3 minutes per reboot (still) on practically any machine, because even though machines got faster, the amount of stuff that wants to load itself on startup has gotten correspondingly greater.Pat Palmer 10:19, 19 January 2008 (CST)
A RAID or stripe set is required. And no, moving the swap file to another drive doesn't make windows boot up faster, because the bandwidth across the IDE/SATA channel is slower between two discs. --Robert W King 11:03, 19 January 2008 (CST)
Robert, I not sure that I agree with this. I have the swap file on my D: drive (right here on my laptop) and it is certainly not a RAID. I know you think it's so, but would you please try it and make sure that you're correct?Pat Palmer 19:53, 19 January 2008 (CST)
To say that you're going to "distribute a paging file across disks" implies that you're allocating an amount of drive space on every drive for a portion of the swap, which requires a stripe or raid. If you're simply MOVING it to another drive all together, no you don't need a stripe then. But that is still a foolish thing to do because when you seperate your system files from the swap, it means now you have to transfer data between two hard drives over the relatively slow IDE/SATA channel and into RAM, versus right from the system disk into RAM. --Robert W King 20:36, 19 January 2008 (CST)
Folks, this article has come along very nicely. Stephen Ewen 23:11, 19 January 2008 (CST)
Thanks for the good words, Steve. Robert and I really have both added a lot to it, and I think it's better because he's been working on it that if it were just me. Despite us not agreeing on everything!Pat Palmer 03:16, 20 January 2008 (CST)
Robert, I see where we are misunderstanding each other now, I think. OK, here's the deal. I can have a part of my swap file on C: and a part on D: if I want to; Windows allows it (all versions of Windows, I do believe). There is no requirement that a RAID disk of any sort be present, only two partitions with different drive letters assigned. Some years ago I noticed that if I put ALL the swap file on a different physical drive that the system files, Windows booted faster. May not be true any longer; disk tech updates all the time. However, there is NO requirement for a RAID stripe to use more than one disk, or a non system disk, as the location of the swap file. So I would like to remove the implication from the article that a RAID drive is required. Perhaps we can find a wording that satisfies you. I really don't see what RAID has to do with this at all.Pat Palmer 23:25, 19 January 2008 (CST)

If the compromise over wording that Pat suggested cannot be reached, might I suggest another possible way forward here?

  • Robert, for now, defer on this matter to Pat, since she is editor. She may be mistaken and has stated so, so this is just a practical step for now
  • Contact User:Greg Woodhouse, a computers editor, and get a third opinion
  • Meanwhile:
    • Very sucinctly state the question for Greg here so he does not have to dig for the issue that needs addressing upon arrival (hopefully)
    • Collaborate, collaborate. Just set this one issue on the shelf for now and go on to other areas of the article. It is really shaping up nicely, it seems to me. If Greg cannot decide the matter, it will be revisitied again prior this article's approval, when the whole article is reviewed.

How's that sound?

Stephen Ewen 01:05, 20 January 2008 (CST)

The text in dispute is the following in "The Swap File" section: "Some operating systems, such as Windows, allow the swap file to be distributed across multiple disks provided the correct hardware is present, such as a RAID channel array, or a stripe set." My claim is that Windows does not require a RAID array to allow users to move or distribute the paging file onto more than one disk, whereas I feel this sentence implies that RAID is required. You can try this on any Windows computer that has a second drive as follows: 1) close any programs 2) open the System applet in control panel, 3) click on the Advanced tab, 4) click the Settings button, 5) click on that popup's Advanced tab. You'll then see where the paging file settings can be adjusted.Pat Palmer 03:03, 20 January 2008 (CST)
Perhaps not (on my part). Do you know if the paging file is considered "one file" on two drives or is it "two files" on two drives? --Robert W King 10:28, 20 January 2008 (CST)
Robert, Windows lets me reserve as much space as I want on as many drives as are present. How it manages them, I don't know for sure, but my impression is that it's then treated, somehow, as one swap file. But I don't know which drive it fills up first or anything like that. I only noticed the speedup when I used NO space on the system drive and lots of space on a secondary drive which happened to be a distinct physical device (not a partition on the same physical device). I always leave at least 64KB on C: (or whatever is the system drive) because Windows likes to use that for error dumps in case of a crash--rare these days, thankfully. I've never known anyone actually to read those error dumps, but presumably one could do so with the proper tools and such. Anyway, I think it's an interesting question of how Windows manages it, and I'd like to know the answer as well. The drives containing part of the Windows pagefile.sys (swap file) have to be fixed drives permanently installed on the computer; they may not be, for example, a removable USB drive. Changing the settings requires a reboot, suggesting that Windows is redistributing the file contents into the newly designated areas (and in fact you can see that on the disk by looking for pagefile.sys after making system files visible in Windows Explorer.Pat Palmer 11:58, 20 January 2008 (CST)
What happens when after placing the swap across two disks, you turn off your computer, and remove one of the disks? --Robert W King 12:19, 20 January 2008 (CST)