# RAM Selection for Server



## jailed (Feb 20, 2012)

Hello,

I'm using OEM computers (Core2 quad) with non-ECC PC RAM for server.

I have Kingston's HyperX RAM on them. They're actually for PCs. HyperX RAM has heat sinks on them.

Currently used ones are 4 GB DDR3 1333 MHz HyperX CL7.

4 GB DDR3 1600 mhz HyperX CL9 is almost half price of that RAM. It's faster but cas latancy is CL9.

Also there's a normal (not HyperX, not have heatsink) RAM that's 1333 mhz and CL9. And almost same price with the second.

I'm using the server for MySQL + Apache. There's about 300 MySQL queries per second and the database is about 20 GB in size.

OS is FreeBSD 8.2

I'm not have problem with current RAM, however I'm developing new applications and I want to scale the servers. I'm not sure which RAM I should go with. I can use 1600 MHz RAM with overclock and so that I can only use one per channel. This is half of the slots. 1333 MHz CL9 RAM has no heatsink but it's more cheaper.

I don't know much about cas latency's effect on servers.

Do you think that my current RAM is worth the price? If I go with overclocked 1600 MHz or 1333 MHz CL9 RAM, will they decrease the performance of the server?

The last question, does ECC RAM affect performance? Do they worth the price?

I wonder your opinions.

Thanks.


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## SirDice (Feb 20, 2012)

If you're going to _add_ the new memory to the current configuration I suggest getting _exactly_ the same speed (frequency and latency) DIMMs as the ones that are already in there.


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## jailed (Feb 20, 2012)

@SirDice,

No, I will buy them for new servers. But I can move the old RAM to new or vice versa. All my servers support 1333 MHz and 1600 MHz (oc).

I will buy a new Cisco Xeon server and it supports 12 DIMMs and 1333 MHz in normal. It supports max 12 x 16 GB RAM.

Low latency RAM and ECC RAM are expensive. I wonder the difference. I'm not able buy all of them and test.

If I buy CL9 RAM instead of CL7, memory size will be almost 1.5x - 2x for the same price.

The gamers choose low latency RAM. My RAM are good for them.

I wonder, if using CL9 or CL7 RAM does matter, or the memory size matters for servers.

Size or cas latency. Which is important for a database server?


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## rajl (Feb 20, 2012)

Is your goal speed, reliability, or affordability?  You get to choose two.

Gamers generally choose speed, with some gamers who have the money willing to spend top dollar for decreasingly marginal rates of return.  Enterprise grade reliability generally isn't a requirement.  If a cosmic ray flips a bit, the chances are that it will be in some unnoticeable and ultimately insignificant manner.  However, latency and frame rates matter, especially with the newer titles played online.

Enterprise servers generally focus on reliability.  If a bit flips due to a stray cosmic ray, the result could be silent data corruption of very important data.  If you need more speed, you buy a faster machine or optimize the software.

I don't know what your requirements are for your individual server.  However, I will give you several general rules of thumb when buying RAM to get the most bang for your buck.  First, buy for size - the more RAM you have, the fewer accesses you have to make to the hard drive, which is exponentially slower in latency and bandwidth.  Second, buy for bandwidth - the price difference is generally less between different bandwidths than between different latencies.  Third, buy for latency.

Note that these are my personal, general rules of thumb.  Obviously application matters.  The amount of memory might not matter to you (e.g. you have a small database or web server with minimal data and content that easily fits into 4 gigs of memory).  Latency might be more important to your application (e.g. response time is critical, and you are serving small files such that you cannot effectively utilize your memory's full bandwidth).


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## Beeblebrox (Feb 20, 2012)

> does ECC RAM affect performance? Do they worth the price?


Yes and *0/1* depending on what you are doing on the server.
ECC RAM is Error-correcting code memory. So, the question "if it is worth the price" depends on what you want your server to serve: Is it a gateway + antivir? then NO. Is it a webserver + php, NO, IMHO. ECC is needed for things that will hurt you: Financial Transactions, Accounting Apps and such. In the end, they all tie back to an sql database ==> you need ECC if you are running a transaction-oriented frontend that has Data Base storage. For example, E-Bay would probably have to have all servers equiped with ECC RAM.

Under certain conditions it is cheaper (and get better performance) to have 2 servers than to place large ECC RAM in one server, and yes ECC, because it double-checks errors does have an impact on performance. As always, all of these are a question of "optimal design" -  about needs, purpose and security concerns.


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## jailed (Feb 21, 2012)

Hello, thank you for your replies.

It's a database server running MySQL and the table type is "memory"

After reading your opinions, I decided to go with ECC registered RAMs. The database is so active and read and writes are equal. It's not for a cache layer for database reads. So, error correction is important.

Thank you for showing me the true way.


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