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    <blockquote> <p>Why is this happening?</p> </blockquote> <p>Welcome to flash.</p> <blockquote> <p>I'm no expert in file IO but I know the fast IO operation times indicate the data hasn't actually been written to disk yet and the big pauses are probably buffers being flushed. </p> </blockquote> <p>Probably not. Most Android devices use the YAFFS2 file system, which does not buffer data too much, as I understand it. However, they do have a per-partition write lock, so your pauses are probably when something else is writing to flash.</p> <p>As more Android devices (e.g., Nexus S) run the ext4 file system, then <a href="http://android-developers.blogspot.com/2010/12/saving-data-safely.html" rel="nofollow">flushing/syncing becomes important</a>.</p> <p>Also, bear in mind that flash write speeds will vary by a variety of other factors, such as how full the file system is, the state of wear-leveling on the particular cells being tried, etc.</p> <p>You may wish to watch Brad Fitzpatrick's <a href="http://www.youtube.com/watch?v=c4znvD-7VDA" rel="nofollow">2010 Google I|O presentation</a> on "Writing Zippy Android Apps", as he goes into more details on this.</p> <blockquote> <p>How do I avoid the pauses?</p> </blockquote> <p>You don't. You move the flash I/O to a background thread, perhaps via an <code>AsyncTask</code>. The new <code>StrictMode</code> in Android 2.3 will help you identify where you have such "janky" code.</p>
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    1. COArgh, that's disappointing. I'd like my undo/redo stack to persist between app sessions so I need to get these stacks saved to disk at some point. Command objects can grow to quite a size as well so I'll need to have a background process writing them to disk as they are created. With unpredictable IO write times though, it's not obvious how I can make sure I get everything written to disk by the time onPause is called if my application is interrupted. The situation is even worse if I need to call .sync() as well on each file. Any advice?
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    2. CO@rebeccamaher: "Command objects can grow to quite a size as well so I'll need to have a background process writing them to disk as they are created." -- a background *thread* please. Consider using a `LinkedBlockingQueue` with a thread receiving mementos on the queue and writing them to flash as they arrive. "it's not obvious how I can make sure I get everything written to disk by the time onPause is called if my application is interrupted." -- your background thread will not be impacted by calls to `onPause()`.
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    3. COOops, I meant thread. Thanks for the references! Aren't there any problems running a thread when another activity comes to the front? Isn't the thread likely to get killed? Thanks for the tips, I can give this idea a try. My only issue is minimising the data to be saved so that, if I cannot save the data to disk fast enough, I won't have to toss too many commands away.
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