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VMounter sample crashes w/ large files

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#16922
Posted: 07/02/2011 07:58:58
by Steve Lawson  (Basic support level)
Joined: 04/11/2008
Posts: 4

cbfs.sys v. 3.1.18.219
Using VMounter (Delphi) example
Install drivers
reboot
Run VMounter
Mount & Add virtual drive.

Dragging smaller files (200MB) works fine.

When dragging large files (700MB) to the virtual drive, Vmounter throws "assertion" and other errors and crashes (NOT bsod).

Is there a maximum file size for this type of operation? (I have searched the CBFS forum for "maximum" and found no indication of a maximum for a copy/move operation).

ALSO - as the documentation states VMounter keeps the files in memory, what happens when the total size of the contents of the virtual drive exceed available RAM? Does it then, perhaps, swap out the Pagefile.sys, or...?
#16923
Posted: 07/02/2011 08:33:05
by Eugene Mayevski (EldoS Corp.)

Quote
Steve Lawson wrote:
ALSO - as the documentation states VMounter keeps the files in memory, what happens when the total size of the contents of the virtual drive exceed available RAM? Does it then, perhaps, swap out the Pagefile.sys, or...?


It does exactly what you see - crashes. Since this is a sample, it doesn't include sophisticated error handling, and this turns into crashes. The goal of VMounter sample is to illustrate how to build a filesystem from files in memory. It is assumed that the developer uses samples as guidelines, not as a production code to take and use.


Sincerely yours
Eugene Mayevski
#16924
Posted: 07/02/2011 09:11:10
by Steve Lawson  (Basic support level)
Joined: 04/11/2008
Posts: 4

I suppose I really SHOULD HAVE STATED:

I had over 1GB showing available when I copied the 700MB file into the virtual container.

FURTHER, if I move SEVERAL SMALLER FILES (ie: 300MB, 300MB, 200MB) into the container, all goes well.

I was simply pointing out a POSSIBLE misbehavior/bug. As I found nothing in documentation discussing memory utilization, I hope you understand my decision to post/ask.

Thank you for your prompt response.
#16925
Posted: 07/02/2011 10:38:22
by Eugene Mayevski (EldoS Corp.)

I believe it's memory allocation issue -- the file is stored in memory as one block and most liley there was no place for contiguous block of 700Mb (or memory reallocation failed).

There are *no* limitations regarding files sizes in CBFS and people work with multi-gigabyte files via CBFS without problems. So whatever could happen is sample's problem, and in this case memory-related one.


Sincerely yours
Eugene Mayevski

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