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I wanted to know what type of memory is consumed when a disk image is mounted in a virtual CD-ROM (for example, when we mount a .ISO file using Daemon Tools) and where is the data inside the disk image stored on a computer when the image is mounted. Also if an image is mounted, will it affect the computer's performance?
Sid
Posted 2015-07-19T14:18:50.967
Reputation: 183
16
It doesn't move the ISO files anywhere. It stays on the hard drive (or wherever it's stored) and when mounted to a virtual disc drive, it just de-abstracts the ISO container.
When the PC reads the first block of data from the virtual disc drive, the ISO mounting application redirects that read request to the appropriate block of data within the ISO file. This process continues for each additional read request.
Geruta
Posted 2015-07-19T14:18:50.967
Reputation: 1 185
2So this should also mean that the size of the ISO file should always be exactly same as the size of the disk in the virtual CD rom – Sid – 2015-07-19T14:42:50.000
5It depends. There is the size and then the size on disk. Because of the way data is stored on hard drives, sometimes a file may take a larger amount of space on the disk then it physically takes on other media. – Geruta – 2015-07-19T14:52:24.800
1(one obvious way to make the "size" and "size on disk" different numbers is to turn on NTFS compression for the file) – user253751 – 2015-07-19T22:03:19.020
@user20574 Turning on compression doesn't always work... If the ISO is badly compressible (e.g. video-DVD) it will just be stored "as-is" regardless of NTFS compression settings. I had some discussions a few months ago with someone who was certain his Windows was broken because NTFS compression didn't give him more disk-space. All the files he wanted to compress where zip/rar archives and/or MKV videos. It took a while to convince him you can't repeat compression on a file and expect the file to get smaller on every run. – Tonny – 2015-07-20T09:09:28.650