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Question about "correct" ImDisk usage/configuration

imdisk configuration

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#1 fzzzt

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Posted 19 June 2016 - 12:53 PM

I love ImDisk and I use it for a few reasons:

  • A RAM-based system %TEMP% folder.
  • High-performance storage for downloads, compiling, or anything else.
  • Avoid slamming my SSDs with tons of writes (browser caches, temp files, etc.).

This is the command I use to create the RAM disk in a Scheduled Task that has a trigger set to run at startup:

imdisk -a -t file -o awe,rem -s 4096M -S 4096 -m R: -p "/fs:ntfs /v:RAM /A:4096 /q /y"

The questions I have (which I didn't see on the FAQ) are:

  1. I recently added "rem" to see if avoiding write caching would be faster, since RAM should be pretty darn fast on its own. Does anyone know if this is true?
  2. Is there a better way to create the RAM disk at startup than a Scheduled Task? I worry that it may not be early enough in the startup sequence. How does the toolkit create disks at startup?
  3. I "aligned" the sectors for performance by using 4K sector sizes, but I really don't know if this matters like it does with aligning partitions on physical disks. Does anyone know if this is useful?
  4. I don't want a file-backed disk, just RAM. The whole point (for me) is to use RAM instead of disk. I use "awe" without an image file so it actually uses physical RAM and not virtual memory. My understanding is that a "vm" type RAM disk could potentially be swapped to physical disk by the system. It this correct and can it be prevented?
  5. When using "vm", it doesn't allocate the RAM when you create the disk, so I don't really know how much free memory my system has. In the past, before "awe" was an option, I created the disk, filled it up with an empty file, then deleted the file in order to pre-allocate the memory... Is there a way to make it allocate the RAM without this when using "vm" type?
  6. The toolkit UI doesn't seem to support "awe" disks, based on the screenshots I've seen. Is this correct?


#2 v77

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Posted 19 June 2016 - 01:42 PM

How does the toolkit create disks at startup?

ImDisk Toolkit uses a dedicated service. The task scheduler is also a service, but it has a lot of tasks to start and check. So in most cases, a command registered in the task sceduler will be started slightly later than in a dedicated service. There is no guarantee that it's always the case, but my tests confirmed this tendency.

My understanding is that a "vm" type RAM disk could potentially be swapped to physical disk by the system. It this correct and can it be prevented?

Yes this is correct, and the only way to prevent that is to disable the swap file.

When using "vm", it doesn't allocate the RAM when you create the disk

All the memory is allocated but the system needs to access each memory page at least one time.
This is a documented behavior:
"The system initializes and loads each committed page into physical memory only at the first attempt to read or write to that page."

Is there a way to make it allocate the RAM without this when using "vm" type?

Remove the -q switch from the format parameters. But of course, this will slow down the ramdisk creation.

The toolkit UI doesn't seem to support "awe" disks, based on the screenshots I've seen. Is this correct?

AWE is supported. See in the Advanced tab: "Use AWE physical memory". This even works with dynamic ramdisks.





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