Memory and Performance

[plan9]

I'm working with a small installation of about 70 users, all using the web client.

I'm running Zimbra on a dual Xeon 2.2 Ghz with 2 GB RAM and RAID 5.

On such a small installation, will adding more memory to the server improve performance noticeably?

Thanks.

[phoenix]

More memory will always help but getting rid of raid5 will help even more.

[plan9]

Really? I had no idea that would create much of a bottleneck. What RAID level will give me the best performance?

[Klug]

RAID 10 (0+1) as stated in the document and multiple posts in the forum.

[plan9]

Okay, I've rebuilt my box to RAID 0+1.

Will installing more than 4 gigabytes of memory be of any benefit? I've read some posts about 2 gigabyte limits and others about problems when exceeding 4 gigabytes.

[phoenix]

If this isn't a 64bit system then you'll have problems with 4Gb, have a look at this post: memory related issue on FC5

[Klug]

Bill, do you know if this 2GB limit only hits FC5 or also CentOS ?

I have a 4GB (quad 700 MHz Xeon) server running CentOS4.4 and Zimbra OSS and have not seen any issue yet.

[phoenix]

I believe it's any 32bit system. There's no guarantee that you'll hit it, I can't remember offhand what triggers it - could be number of connected users.

[plan9]

The ZCS Installation Quick Start guide lists a 2 GB minimum, but a 4 GB recommended RAM configuration. I suppose the 4 GB applies to 64-bit processors.

[KevinH]

64bit gives you more headroom than you need with memory. The key difference in 32bit v 64bit with respect to memory is how much memory a individual process can take. So MySQL, Tomcat(java), etc in a 64bit env can use more than 3GB each. So moving to 64bit will let you cache more data in memory which will give you a nice performance boost on a busy system assuming you add more RAM. Having more than 4GB of RAM on a 32bit system usually doesn't help too much other than file system caches.