Everybody remember the introduction of the local workspaces in 2012, enabling offline scenarios with Team Foundation Server. But did you know they have a limit on the number of files prior to performance degradation?
This limit is 100000 elements.
TF401190: The local workspace temp_WS;User has 248536 items in it,
which exceeds the recommended limit of 100000 items. To improve
performance, either reduce the number of items in the workspace,
or convert the workspace to a server workspace.
There it is. It’s not a bug, but it is a design choice by the Team Foundation Server team.
Local workspaces work leveraging the content of the hidden $tf folder, which tracks all the changes for a file (deltas) from check-out to check-in. That’s how you get features like Candidate Changes. The side effect is that despite the source copy is compressed, it is still a copy, hence you have a physically bigger workspace.
The workarounds in this case is to use a server workspace (easy) or to split the huge, monolithic workspace into several smaller workspace so you won’t hit the issue. This could be harder than just using a server workspace, but with a bit of planning it is absolutely feasible.
This post by Philip Kelley is extremely enlightening, as it is a deep comparison between local and server workspaces. Right there he explains the differences, and how they are implemented (the PendChange permission, the +R bit, etc.).