Google Drive for desktop: the drive letter shows the cache volume's free space, and deleted files count against quota

Observed June and September 2026 with Google Drive for desktop in streaming ("Stream") mode on Windows. The app version was not recorded.

The drive letter shows a local volume's space, not cloud quota

In streaming mode Drive appears as its own drive letter (here G:). On both machines the letter reported the capacity and free space of a local volume rather than the account's storage:

• On the first PC, the Drive letter showed 0.4 GB free, exactly matching a separate 1.9 TB data volume that was 99.98 percent full. The Drive content cache had been relocated to a folder on that same volume (about 440 GB at the time).
• On the second PC, with the cache at its default location, the Drive letter reported the same total size (238,973,612,032 bytes) and about 222 GB free as the system volume, C:. A free-disk retention rule written against the Drive letter therefore measured the system disk, which the footage did not consume, and a first estimate of how long recordings would last was wrong by that mistake. Real usage was in the Drive cache (about 19.5 GB at that point), with the data itself cloud-only.

The common factor is the volume holding the Drive cache, so the letter's figures appear to follow the cache location. That relation was inferred from two cases and not checked in Drive documentation. Quota (what the account may store) is shown only on the Google account's storage page; for a folder owned by another account it could not be read through the connector that session used.

Uploads fail with "not enough space on the disk"

On the first PC, copying a large tree to the Drive letter with robocopy failed with:

not enough space on the disk

The session's explanation: Drive stages each file in its local cache before uploading, the cache lived on the full volume, and so staging had no room. The error was about the local volume and not about Google quota. The proposed fix was to move the cache with Drive for desktop, Settings, Preferences, the second cog, "Local cached files directory", to a volume with free space; Drive restarts and migrates the cache. The same step would free the 440 GB on the full volume. Whether the robocopy then completed was not recorded, so the fix is untested here. The session also warned that copying into a streaming drive forces local materialisation and upload of every file, which is slow and fragile for hundreds of gigabytes, and that the real free cloud quota had to be checked first.

Deleted files and quota

For a retention job that deleted old day-folders from a streamed folder, the script's comment states that deleted files go to the Drive Trash, still count against the account quota until purged, and that Drive purges the Trash automatically after 30 days, so the real footprint is about retention plus 30 days. This came from the session's own knowledge, set down as a comment in the script; it was not measured and not tied to a vendor page here.

Practical effect on pruning scripts

A pruning rule for streamed Drive content that keys off free disk space on the Drive letter does not measure quota. The second session replaced a free-disk rule with an explicit size budget for the folder (the Drive letter reported 222 GB free against an account that had several terabytes), plus a ceiling that trims the oldest folders first.