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My HDD is slow 5400RPM and when working with 10GB size files it is impossible to use the computer until that big file finish re-creating a new copy/muxing/writing/etc. depends on process, the thing is it eats up all HDD speed and no other program can be used while this process runs.

So I was thinking maybe I could limit HDD write speed for programs I work with, so then it would reserve free HDD leftover speed to use for browsing internet or playing mp3s while the big files are being processed.

user3108268
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    I've never heard of a throttled HDD IO in Windows, at least natively. Have you tried setting the process *priority*?: `wmic process where name="calc.exe" CALL setpriority "idle"` – Marcelo Aug 11 '14 at 16:33
  • @Marcelo Priority dictates CPU time, not disk. When processing a large file, the disk is what is slowing the computer down, not the CPU. – Keltari Aug 11 '14 at 19:09
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    Related: http://superuser.com/questions/462541/how-to-limit-disk-usage-write-i-o-by-application-not-space-usage – Cees Timmerman Aug 11 '14 at 19:19
  • @Keltari Yes, I'm aware. I just thought that maybe modifying the priority for CPU could have *some* impact towards the final objective in the question. – Marcelo Aug 11 '14 at 19:27
  • @Marcelo It would have an impact, true. But it might not necessarily be for the better. If the computer was also swapping memory, then it would heavily decrease the performance. – Keltari Aug 11 '14 at 19:29
  • Things you need to know about having multiple programs using the disk at once: http://stackoverflow.com/a/7640319/103167 and http://stackoverflow.com/a/1240473/103167 – Ben Voigt Aug 11 '14 at 19:42
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    If the computer is "unusable" when copying huge files, is it possible that you have forgotten to enable DMA? Normally, whether or not the disk is busy makes little or no difference since that happens without much (or any) CPU intervention. – Damon Aug 11 '14 at 19:45
  • It is possible by setting the Background priority, according to [dsulimano](http://superuser.com/a/462576/140956) – niutech Aug 11 '14 at 21:45
  • @Marcelo: Some programs (like Diskeeper) can throttle their own I/O, so I suppose this can be done by writing a filter driver. But it's a difficult thing to get right, and even more difficult to get working *well*. – user541686 Aug 12 '14 at 06:55
  • @Mehrdad I would think that such throttling would happen above the I/O, in the application. As in scheduling the buffers/blocks to be written to disk at the application level. – Marcelo Aug 12 '14 at 12:33

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Unfortunately, you can't do that. Hardware is abstracted from applications and even parts of the OS. In essence, the application says "write this to disk" and the OS handles it. The application doesn't handle how or even when it gets written. All of this is handled at the driver and kernel level and there is no real way to change this.

Even if you could do this, the fact is you are using a spinning magnetic disk - and a very slow one at that - you wouldn't see much gain. The drive is constantly spinning and the heads are moving along the disk. Even if you wrote to your file less, the disk will constantly be seeking the right areas on the disk to read/write to/from.

Your best option would be to get another drive and do your work on that drive, leaving your first drive for your internet, MP3s, etc.

P.S. You didn't mention how much RAM you have. Swapping could be a factor in the slow speed. Depending on how much RAM you have, adding more will only help.

Glorfindel
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Keltari
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    Wouldn't a Windows version of Linux' `ionice` come close to being an answer? – Daniel Beck Aug 11 '14 at 19:08
  • @DanielBeck There may be software out there that might work. However, who knows what complications might come from using it? It would be *so* much easier to just slap in another drive and be done with the issue. – Keltari Aug 11 '14 at 19:12
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    You can do it. See the [dsulimano's answer to a similar question](http://superuser.com/a/462576/140956) – niutech Aug 11 '14 at 21:47
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    I don't see any principled argument to why an application could not be throttled. Here's a very simple throttle: Suspend the process for 1sec every second. That throttles IO by about 50% and lets other processes slip in to use the disk. Seek times are on the order of 10ms. – usr Aug 12 '14 at 00:09
  • @usr: It depends on the type and frequency of I/O. Your approach works in some cases but not others -- e.g. if the I/O is happening entirely in kernel mode, I don't think you can always pause it by pausing the user-mode process. – user541686 Aug 12 '14 at 06:57
  • @usr A reasonably written application on a system with disk DMA I/O enabled will need almost no CPU time for itself during the work - the copying itself is handled not even by the kernel, but by the actual hardware. The only point where you need any CPU time at all is at the buffer boundaries, which might or might not happen often enough for suspends to be effective. – Luaan Aug 12 '14 at 07:29
  • @Luaan yes, but a suspended app cannot issue more IO requests. The old ones complete, and then there is a pause. This was just an example to show that throttling IO is possible in principle. It's just not built-in to Windows, but many techniques for doing that exist. You can even extend Windows with a driver to do that. – usr Aug 12 '14 at 10:12
  • Here's a link to an article in Russian, the author has built an utility which integrates into Explorer context menu: https://habr.com/ru/post/317802/ The sources is .REG file (i.e. the utility is a simple registry tweak), it is posted in the article. – Alexandr Zarubkin Mar 25 '19 at 11:18
  • @DanielBeck you are correct. The Sysinternals Process Explorer can perform the same functionality as the nice and ionice utilities under *nix variants. This answer is plain wrong. Setting the process to background 4 priority is the correct way to achieve the desired result of low I/O and low CPU priority. Both combined significantly reduce the system impact of these processes. This is the real way to change this. The low memory priority should also throttle any disk swapping taking place as well, another hidden factor that can easily affect system responsiveness. – Ian Macintosh Jan 30 '20 at 20:53
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Process Lasso allows you to prioritize I/O. From their FAQ:

New in v4.1 (v4.09 beta), Process Lasso has explicit current and default I/O priority settings available those who require them. This only applies to NT6+ (Vista,Win7,...).

HOWEVER, Vista's I/O prioritization is based on the priority of the thread doing the I/O, which is dependent on the priority class of the process doing the I/O. There are actually only two levels of priority usable by applications, Normal and Very Low. Although there are technically 5, only these two are implemented or usable by processes.

Therefore, adjustment of the thread priorities will propagate to the I/O of that thread. In this way, Process Lasso already does I/O prioritization. Microsoft recommends applications adjust their I/O priority based by setting the calling thread's priority (directly or by adjustment of the process priority base class).

See also the paper on I/O prioritization from Microsoft.

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niutech
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Use the Sysinternals "Process Explorer" to set the priority to 'Background: 4 (Low I/O and Memory Priority)'

Find the process that is using Disk I/O by right-clicking the Column Headings and under Process I/O add the column I/O Delta Writes. Then click on that column to sort by it, and the offender is likely to be the top process. Whatever way you use to find the process, then right-click the process and set it to Background: 4 priority.

Subsequently right-click the process again, go to Properties and look at the Performance tab and you should see I/O Priority set to Very Low.

This would be the equivalent of using nice and ionice under Linux.

You should find a significant improvement to the system performance and responsiveness after doing this. You will have to re-do this after rebooting and/or after the process exits and restarts.

Ian Macintosh
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What I do when I have a process that keeps eating all my disk I/O on Windows is bringing up Process Explorer and pausing the offending process. After I'm done with my business and am ready to wait a bit I resume it. It's definitely not the most productive way of doing it since it's all-or-nothing way of controlling disk I/O and your process will have to wait while you use your computer, but so far I haven't seen any better alternative.

On the other hand, if you can do your process on Cygwin, you can install pv on your computer and use it as the first or final step with an option (I think it's -r) to throttle pv's output rate.

RAKK
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