Game updates using slow SSD for no reason

[Seth NoWai]

Hi. I have been for a while observing weird issue with Steam downloads using slower of two SSDs for absolutely no reason.

So I got two SSDs, one is fast NVMe and that is C drive. Other one is older SATA SSD that is D drive I kept for storage and few more games. Because why not, it is from my old PC. And Steam has two libraries, one for each disk. C one is primary, D is there mostly to move games out of the way, if C is full.

But weird thing about it is that whenever Steam is updating games installed on drive C, faster one, it downloads files to slower D drive, then unpacks them to C drive. Which basically caps D to 100% load and takes longer. Like right now it is installing Oblivion Remaster 15GB update for 10min. CPU isn't capped, just SSD is and that is bottleneck. Downloading was done in first few minutes, I got 1000/100Mbps connection.

Now I know it isn't doing it due to free space as C has 175GB free and D has 110GB free. And both have sufficient space for 15GB update.

So my question is, why isn't Steam using drive C, where game is installed and has sufficient space to download update and install it faster? And is there any way to change this? I don't want to keep adding and removing D drive library. And it would be really nice if I could set my preferences about it.

Don't get me wrong, the way it works is great to split load between two SSDs with same performance, but in my case they aren't. And before this started to happen, updates would install much faster and they do, if I only use C drive. I do cut D bit of a slack here, it is old drive and for what it is, it works fine.

Here are screenshots:
Task manager with D at 100% load: https://file.si/DYxK/screenshot-2025-06-11-234351.png
Steam showing it is only installing update, downloading done: https://file.si/0Qp2/screenshot-2025-06-11-234416.png
Free space on disks: https://file.si/zRNx/screenshot-2025-06-11-234533.png
Showing game is on C and that is my primary library: https://file.si/xR3m/screenshot-2025-06-11-234602.png

[HIVEmind]

Set your default drive in steam.
Make sure space is available.

[flingo]

Go to Steam > Settings > Storage and remove the D drive temporarily. That way Steam will be forced to use C for updates too. After the update’s done, you can add D back if you want.

Sadly, there’s no way to tell Steam “always use this drive for temp files.” It just does its own thing.

[Satoru]

Steam will default to where the game is installed to update a game

HOWEVER

If that drive does not have enough space, steam will instead stage updates on a different drive that does have space.

Steam also does not want your patching to make the drive fall too low on disk space. Meaning that even if you 'have enough', if the free space while the patching is happening is too small, it will defer to the other drive