When looking into buying a NAS (network drive), would it benefit from more RAM or more CPU power?
(Hello again :)
Based on personal experience, you'll need at least 1GHz ARM processor (probably Marvell Kirkwood series) to get speeds greater than 50MB/s. Intel processors are generally faster, but also more expensive and power hungry.
256MB RAM is the minimum. You can get very good performance from it if the software is highly optimised (e.g. Synology or Qnap's proprietary system). High-end NASes, especially ones with Intel chip or the 1.6GHz Kirkwood, uses 512MB or more RAM to provide speeds around 100MB/s (i.e. almost saturates the physical gigabit ethernet link). Of course, there are Small Business servers that can run other applications and you'll need more RAM for that.
If you want to get something greater than 30MB/s from your setup, make sure you check the quality of your ethernet card (on your own computer and the NAS), the cables and the switch. You'll probably need 9K jumbo frame to get the CPU usage down, so make sure it's supported on all the devices.
The disks have to be fast enough as well. The WD Caviar Green ones have a long spin-up time so better avoid them.
smallnetbuilder.com is a good place to go to.
Depends entirely on what you are using it for.
The more/faster, the better, but, it depends... there will be a point where faster will not help.
For example, if you have a 100Mb network card, and it is serving files at ~20Mb whilst the memory/cpu are at 100%, then, obviously the memory or hard drive are the bottleneck.
If however you are serving anywhere up to 80Mb on a 100Mb card or around 700Mb on a 1000Mb card, then, these are good speeds and I doubt you will get much more from upgrading the other hardware.
If you are searching for premade NAS units, it is really hard to say what you need as some may have much more efficient usage of memory utilization. I suggest you look up reviews.
Also, if there is software raid being used, this can be heavy on CPU usage.
RAM. A storage server doesn't need much of either, but if you have more RAM good software on the server can use it to cache frequently read files for faster responses to read requests.
That said, the most common solutions don't really take good advantage of the extra RAM: the embedded hardware devices expect a specific amount and wouldn't know what to do with more or less. The operating system -based options (Windows Server, Windows Storage Server, and linux-based file servers -- even NAS specific distros like freenas and openfiler) don't do a lot to improve on the basic operating system caching, which doesn't optimize for file access in this way.