Please check the status of this specification in Launchpad before editing it. If it is Approved, contact the Assignee or another knowledgeable person before making changes.


Use a new write cache mode for removable drives which combines the performance of write caching ("async" mode) with the intuitive and saver behaviour of the "sync" mode. Sync mode is inappropriate because it is unacceptably slow and has a fast flash wearout, while async mode takes a long time to flush the cache after unmounting, which caused us to add mitigations like "please do not remove" notifications.

Ideally write caching stays enabled, but the cache is flushed already when closing a file, not when unmounting a drive.

Release Note

This section should include a paragraph describing the end-user impact of this change. It is meant to be included in the release notes of the first release in which it is implemented. (Not all of these will actually be included in the release notes, at the release manager's discretion; but writing them is a useful exercise.)

It is mandatory.


Write caching on removable devices is one of the primary causes of data loss among novice Ubuntu users. This is primarily because on Windows the cache gets flushed immediately after saving a file, and even though it is recommended to first unmount the devices through the appropriate icon in the systray, many users just remove the usb drive as soon as they're done copying the files, and in 99% of the cases it doesn't cause any problems. Repeating this behavior on Ubuntu will result in severe data loss and sometimes file system corruption.

Use Cases



You can have subsections that better describe specific parts of the issue.


This section should describe a plan of action (the "how") to implement the changes discussed. Could include subsections like:

UI Changes

Should cover changes required to the UI, or specific UI that is required to implement this

Code Changes

Code changes should include an overview of what needs to change, and in some cases even the specific details.



  • data migration, if any
  • redirects from old URLs to new ones, if any
  • how users will be pointed to the new way of doing things, if necessary.

Test/Demo Plan

It's important that we are able to test new features, and demonstrate them to users. Use this section to describe a short plan that anybody can follow that demonstrates the feature is working. This can then be used during CD testing, and to show off after release.

This need not be added or completed until the specification is nearing beta.

Outstanding Issues

This should highlight any issues that should be addressed in further specifications, and not problems with the specification itself; since any specification with problems cannot be approved.

BoF agenda and discussion

Use this section to take notes during the BoF; if you keep it in the approved spec, use it for summarising what was discussed and note any options that were rejected.


  • 30/10/2007 [AlwinGarside]: I think it's important that the cache gets flushed BEFORE the copy/move progress window (in GNOME/KDE/XFCE) disappears, if this is not possible using the proposed method of write caching/flush on file close than imo file caching should just be disabled for removable devices. Actually for Floppy Disk Drives I suggest we just disable write caching right away, not much of a performance impact there.


RemovableDrivesCaching (last edited 2008-08-06 16:26:20 by localhost)