Comments on: Upgrading to a 64-bit SQL Server 2005 environment

By: naterw

naterw — Thu, 05 Mar 2009 17:20:53 +0000

32 bit or 64 bit the rules for memory are the same really. Watch your page life expectancy counter primarily and if it’s very low (below 300) you need more memory, if it’s very high (hundreds of thousands) you could make due with less memory.

As a general rule for my systems I like to keep memory equal to roughly 50% of the database size. Anything less that this and the PLE tends to nose dive very quickly. This, of course, assumes that you’re not storing large quantities of infrequently accessed data. It would also depend on the usage of the server, a data warehouse should probably be higher than that depending on access frequency, an OLTP server you could get away with lower numbers.

By: supercoolmoss

supercoolmoss — Tue, 03 Feb 2009 22:45:44 +0000

Can you suggest a minimum amount of memory to handle the 64-bit OS, application & two or three instances?

As a minimum, I’d suggest starting with a similar amount of RAM as you’re using on the existing 32bit environment(s) and compare performance under load.

I wouldn’t correlate memory with the amount of CPU cores. Instead you should consider the current and future database(s) sizes and the number of user connections to these databases. Memory is cheap comparatively, so it’s probably OK to slightly over-estimate!

Regards,

SCM.

By: dschwant

dschwant — Mon, 02 Feb 2009 21:05:06 +0000

Like I said “This is so general, though, that you will get a lot of people questioning it.” My take is that, with the price of RAM, put in as much as the thing can fit. If you are doing a significant amout of re-reads in IO, the performance impovements you get from having it cached are very impressive, and the goal in performance improvement is to remove the bottlenecks. But, it is like playing “whack-a-mole” as once one is dealt with another one will crop up.

I guess since I am used to working with very large databases, my recommendations will be on the top end. But, as I said, the only way to really know what you need is to analyse and understand your environment. Noone can give a good recommendation without knowing a lot of mroe details.

So, if you just want a recommendatuion with no analysis, then, “Damn the torpedoes! Full speed ahead!”, give it 24 GB per core !

By: mrdenny

mrdenny — Mon, 02 Feb 2009 20:01:54 +0000

12 Gigs per core, that’s a ridiculous amount of RAM to recommend that someone purchase. Where did you get this number from?

How can you recommend an amount of RAM for a system without knowing how big the database will be? Just because a database is clustered doesn’t mean that it is a large database. It could be a critical system that is only 10 Gigs of data on an 8 core system. Why would someone on a system this size need 96 Gigs of RAM? That’s just a waste of RAM.