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ventoy / Ventoy

A new bootable USB solution.
https://www.ventoy.net
GNU General Public License v3.0
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Support compression #817

Open TPS opened 3 years ago

TPS commented 3 years ago

@ventoy All the listed currently-supported disk image formats are typically uncompressed, which is wasteful when supporting multiple disk images on an often limited-space USB drive. Could compression be supported in @ least 1 of these ways?:

ventoy commented 3 years ago

As I said in #645 Ventoy depends on the file's location on the disk and map these blocks to a virtual device. So the file in the filesystem can NOT be compressed. So brtfs and other filesystems with compression enabled can NOT be supported.

TPS commented 3 years ago

@ventoy Are the rest possible?

whocares0101 commented 3 years ago

How about mame chd support? https://github.com/rtissera/libchdr

HaleTom commented 2 years ago

For other Googlers, to find this issue:

error: module `ntfscomp` isn't loaded
error: read MFT 0x53 fails.

Work-around: You don't need to uncompress the whole drive, just the .iso itself, or perhaps the folder containing your boot ISOs :)

derzahla commented 1 year ago

cant img/iso files compressed with various tools be uncompressed to a ramdisk and treated the same as uncompressed images? That would be a great feature

HaleTom commented 1 year ago

@derzahla that's a good idea -- feel free to raise it as a separate issue :)

Even so, the ISO couldn't be loaded into ramdisk as per your suggestion because of this current issue: the data in the ISO couldn't be read if the ISO was compressed and residing on NTFS.

polarathene commented 1 year ago

Ventoy depends on the file's location on the disk and map these blocks to a virtual device. So the file in the filesystem can NOT be compressed. So brtfs and other filesystems with compression enabled can NOT be supported.

Is there a particular resource that clarifies this limitation?

I would have thought that the filesystem was responsible for managing it's data and how it compresses and stores the extents of a file. Other software would just take the file and could modify any part of it completely oblivious to filesystem features like compression, without any issue.

What is different with how Ventoy approaches it?

A 128 GB fixed size .img (with a linux OS install) compressed to 7GB disk usage on host BTRFS (with compression enabled) disk, but without using specialized utility like compsize, most generic software still considers it as 128 GB file.

I would have thought that Ventoy would map the 128GB file as per usual, and BTRFS would handle the compression behind the scenes without any issues/differences?

I tried to look up compression limitation with device mapper but wasn't finding any helpful results :(

Interpause commented 2 months ago

When ntfs compression is used on the iso, i get this error instead of ntfscomp isnt loaded:

error: Unsupported chunk list
.
error: image chunk is null
.

i think both errors should be added to the faq, and the installation guide should also indicate compression isnt supported