Hardware for EROS?
Sat, 29 Apr 2000 12:44:18 -0400
> I agree. The military seems to be interested in the exotic
> because they want instant-on. I don't care about
> instant-on; but for
> distributed computing, I'm desperate for low latency stable
> storage so that
> I can do instant commit. Then, I could afford to have
> machine X not release
> message M until the state that had computed message M had
> been committed to.
Looks like I am very late getting to this email, but I thought I would
contribute this info anyways.
Droplets, using my Acid database, uses the "don't reveal state to
external entities until you've committed that state" model. This was a
pretty significant performance problem until I implemented journaling
in my Acid database.
With journaling, it takes about 20ms to commit the state produced by a
single message. Compare this to the approximately 200ms I lose on
round trip latency over the internet and the approximately 2s response
time that the typical web user is accustomed to.
With some more engineering, I might even be able to improve on the
20ms commit time, but why bother?
Another interesting thing to note is that the journaling actually
improved overall system performance as well, since I can merge message
commits, and sort them, before writing them into the main application
Now on to more difficult problems like, "What if my committed state is
struck by lightning?" I don't have numbers yet for the "don't reveal
state to external entities until you've committed and mirrored that
state" model; however, I suspect that even it will work without
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