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We just got a nice new server (our future email server)
This is how it got shipped to us.
2 2.66Ghz Quad Xeon
24 GB RAM
8 Harddrives configured in RAID 10 total disk space 1TB
The email system we will be running (Axigen) doesn't support 64 bit yet (next year) so we're currently running the 32 bit version. It is my understanding thought that Fedora Core 6 only supports 16 GB RAM. (We had ordered the server with 16GB of RAM and got 24 GB) However, I could only see 2.5 GB using the "top" command. So I removed 8 GB to bring it down to 16 GB, however, I can still only see 2.5GB. My kernel version is 2.6.22.9-61.fc6
What do I have to do in order to use at least 16GB of RAM?
The bios is reporting the full amount, but not the OS.
The "SMP" kernel supports a maximum of 16GB of main memory. Systems with more than 16GB of main memory use the "Hugemem" kernel. In certain workload scenarios it may be advantageous to use the "Hugemem" kernel on systems with more than 12GB of main memory.
is there a bigmem or hugemem kernel available for your distro ?
Not that I can find. I found a generic source kernel for Red Hat so I'll see if that works. I read the second quote as well, which is why I downgraded to 16 GB. Note: it is Fedora Core 6
I couldn't figure out how to compile the hugemem kernel for RedHat on Fedora, but I found a hugemem kernel for Core 2. However, this kernel gives the following conflicts.
kernel < 2.6.17 conflicts with hal-0.5.8.1-6.fc6.i386
kernel < 2.6.13 conflicts with kudzu-1.2.57.6-1.i386
kernel < 2.6.17 conflicts with autofs-5.0.1-0.rc3.33.i386
kernel < 2.6.12 conflicts with initscripts-8.45.3-1.i386
I also, downgraded again to 12 GB and still only see 2.5 GB of RAM
Re-compile the present kernel with 64 GB support. A program can always be recompiled for 64-bit. It may or may not work reliable or be efficient. Another way is to setup another root to run 32-bit programs under the 64-bit OS. I recommend stick with 64-bit OS because it will utilize the RAM better than 32-bit with PAE.
I suggest use CentOS because it is a lot better for security than Fedora. If you want a lot more security, setup Gentoo with SELinux and harden. If you use Gentoo, you do not have to worry about X11 being loaded which increases the vulnerability of the server.
For a e-mail server, I would setup the hard drives in RAID-15. It will provide multiple writes and multiple reads. Of course two hardware RAID controllers have to be used and then be mirrored using Linux.
Fc6 support will be dropped in about two months (no more official updates). The current support life for any version of Fedora is about one year. For desktops that is ok but for servers it is a PITA. Centos5 is RedHatEl5 with the logos removed. It has a 5 year support life(with 4 years of that left). It is very similar in feel to FC6. Other than the upcoming lack of updates for FC6, there is minimal differences in security.
With anything above 3gig I would strongly suggest 64bit. You SHOULD be able to use the 32bit versions of most libs for those apps that do not have a 64bit version. For example you can run the 32bit version of Firefox on 64bit Fedora (and many do).
Fc6 support will be dropped in about two months (no more official updates). The current support life for any version of Fedora is about one year. For desktops that is ok but for servers it is a PITA. Centos5 is RedHatEl5 with the logos removed. It has a 5 year support life(with 4 years of that left). It is very similar in feel to FC6. Other than the upcoming lack of updates for FC6, there is minimal differences in security.
With anything above 3gig I would strongly suggest 64bit. You SHOULD be able to use the 32bit versions of most libs for those apps that do not have a 64bit version. For example you can run the 32bit version of Firefox on 64bit Fedora (and many do).
The reason I'm using an older version of Fedora is because I found it more stable than the newer versions. As stated earlier, the email program we're using does not support 64bit OS's. It just isn't stable yet. The main updates I'll be needing are the spam assassin and clamav updates. The server is behind a physical firewall so if that isn't secure enough nothing will be. Clamav provides their own updates and so does Spam Assassin.
The app does not have to support 64bit OS. You install the 32bit libs on the 64bit OS (the same libs used on the 32bit version of the OS). That is why I mentioned the people running 32bit FF on 64bit OSs.
The reason I'm using an older version of Fedora is because I found it more stable than the newer versions. As stated earlier, the email program we're using does not support 64bit OS's. It just isn't stable yet. The main updates I'll be needing are the spam assassin and clamav updates. The server is behind a physical firewall so if that isn't secure enough nothing will be. Clamav provides their own updates and so does Spam Assassin.
The free version of Axigen only supports 5 mailboxes if I'm reading that right, and from the beefiness of your server I'm guessing you have more than 5 users..
Have you looked at Zimbra ? it does everything Axigen does as far as I can see (including spamassassin and ClamAV) but the free version of Zimbra isn't limited to 5 mailboxes..
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