Why is the "ci_sessions" table type MyISAM?

[eluser]sqwk[/eluser]
[quote author="WanWizard" date="1280879058"]
We use a modified sess_write() method, that skips the write. We do an explicit write after the page request has been processed and the output generated, so only one session update per page request. That reduced the number of update queries by over 90%.[/quote]

Wan, could you post that modified sess_write()? Any disadvantages?

P.S: Sorry to roll up this old post.