Do sweepers work across app servers?

If I had a dozen App servers and one DB would my all my app servers be
notified via sweepers when a given representation was updated? If not
what cache expiring mechanisms are there that can be used across multi
app servers?

If I had a dozen App servers and one DB would my all my app servers be
notified via sweepers when a given representation was updated? If not
what cache expiring mechanisms are there that can be used across multi
app servers?

No. I'm assuming you mean you are caching a page to disk on several separate servers and then something on that page changes and you expire it, will all servers expire it. No.

You could use a central memcache store, but that won't be as fast as page caching. Or you can have each app server use a central disk (SAN, etc.). Or you can write something that tells each server to expire a page. Perhaps by overriding expire_page().

-philip