RemovableDrivesCaching

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Summary

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

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It is mandatory.

Rationale

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

Assumptions

Design

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Implementation

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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.

Migration

Include:

  • 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

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

Outstanding Issues

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BoF agenda and discussion

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Comments

  • 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.


CategorySpec

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