Is there any sense running ext3 (journaling fs) on top of what the host is running (most likely a journaling fs + raid)? Won't this slow down the disk I/O of the linode?

Running ext3 (or the like) will keep your files in a sane state when and if a crash occurs; it provides the same benefits as running ext3 on a "real" machine. There is more overhead with ext3 vs ext2, but under some workloads ext3 can be faster than ext2 (here we go ).

Side note: Recently Jeff Dike (UML author) has been working on mmap'ed ubd device driver; which saves having to copy blocks/pages around which pollutes the cache and is less efficient than the mmap solution.

Are you seeing a performance problem?

-Chris

I was just thinking out loud. I'm not having any performance problems with disk I/O.