ISPConfig does not consume any ram as its no service that rusn permaenatly. ISPConfig consumes just a few magabytes once a inute and while you use the ispconfig interface. So the memory consumption you refer to is the consumption of services like apache, postfix, amavisd, dovecot etc. and yes, 900+ MB is absolutely normal for a full email, web and dns server.
I am running IPConfig on a PIII 1ghz with 512mb ram (HP e-pc 40) using CentOS 6.3 with Postfix/dovecot/apache, and it works fine. But what you will see is that linux will use unused RAM for cache, so if you do a free -m it will show you whats being used including cache. If you take away free, shared, buffers and cached from the total it will give you the amount of RAM actually being used by by the OS and apps. In the below i have about 205MB of RAM used. [root@tui ~]# free -m total used free shared buffers cached Mem: 498 459 39 0 61 193 -/+ buffers/cache: 203 294 Swap: 1022 23 999
