I'm experiencing the same problem, but not in a cluster environment.
1. There is a way to deploy without unpacking; see
https://glassfish.dev.java.net/downloads/quickstart/index.html#ProcedureTo_Deploy_From_a_Development
Apparently, though, this does not work in a cluster environment (according to the recent post from hzhang_jn).
2. For me, at least, this does not help. My war (16 Mb) takes about 1.5 minutes to deploy from a .war file and over 3 minutes to deploy from a directory (that's right -- directory deployment takes *longer*).
Good luck. Hope you find some solution; for my part, I'm going to use Tomcat for development and deploy to GlassFish only when I've finished changing things.
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