Why does steam require so much free space to update stuff?

[Kim the Rocker]

So as the title says why does steam need more than (and allocate all of it) 8gb to dl a 1gb patch. Is it a problem with steam or is it a problem at my end?

[aiusepsi]

It's to do with the size of the files that are modified.

There's no great way to insert data into an existing file (without, for example, causing file fragmentation) so Steam recreates a new patched file from bits of the old file that are unchanged, and new downloaded bits.

So in your example, even though the new bits are only 1 GB, they're part of 8 GB of modified files. This is, incidentally, much better than the old Steam system; that'd just go ahead and download 8 GB. In principle, Valve could add an option to revert to the old behaviour, but I don't think many people would be happier with that. Game developers could also modify their packaging scheme so that fewer, smaller files are modified when a patch occurs.

[Satoru]

Here is how the new SteamPipe patches work

1) A small delta patch is downloaded to your computer
2) From this small delta patch, the system compares the patch to all the target files.
3) The new patched files are recreated by analyzing both the original file, and the patch file
4) The new target files are copies back to the game directory

Thus it's possible for Steam to download a 1KB ptach, but to need say 5 GB of disk space because the target file being patched is 5GB large.

Before Steam would download the entire file again. This meant that if a 5GB file was patched you had to download 5GB, even if only a tiny tiny amount in the file was actually changed.

The new system trades bandwidth, a finite and costly resource for most users, for disk space, a more flexible and low cost resource.