building a nas

[stainremover]

trying to build a low budget nas to do backups to at home. i definitely want reliability (e.g. redundancy) with performance coming in a close second. the network at home is gigabit. i was wondering whether or not it is worth it to:

(1) get a 3rd drive to run a raid 5 to improve performance.
(2) get a raid controller to offload the parity processing.

my budget is a bit tight and i'm really concerned about power consumption. i'll be using wd greenpower drives. my main concerns are:

(a) how many computers would i have to transfer from in order for hard drive speed to be a bottleneck (i.e. that i would actually benefit from the striping in raid 5)?

(b) the proc will be a celeron 430. if i do end up going with a raid 5, would the processor end up being the bottleneck? i don't think i'll be doing anything on it outside of backups.

[Mathemabeat]

I run a celeron 420 in my fileserver and get about 50 to 60 megabytes/sec transfer rate from my desktop to the fileserver across gigabit. This is single drive to single drive transfer. No arrays involved on either side.

I would imagine the celeron 430 would be more than adequate for parity calculations on software raid 5 array.

[Syntax Error]

Write speeds are going to be slower than RAID 0, if that's what you're using currently, because of the parity calculations during the writes, regardless if you use software based RAID 5 or controller-based, that's just the nature of the beast.

As for the distributed load across multiple computers, a good RAID 5 should be able to get decent read speeds (i.e., 100MB/s+), but of course, Gigabit Ethernet would cap out about ~125MB/s or so (depends on the quality of the NIC, switch, and other factors, of course).

As for the Celeron, if you get a decent hardware-level controller card, that should pretty much be a non-issue, since hardware-based RAID is regulated by the controller, which has its own built in processor and memory to do parity calculations.

[stainremover]

Write speeds are going to be slower than RAID 0, if that's what you're using currently, because of the parity calculations during the writes, regardless if you use software based RAID 5 or controller-based, that's just the nature of the beast.

As for the distributed load across multiple computers, a good RAID 5 should be able to get decent read speeds (i.e., 100MB/s+), but of course, Gigabit Ethernet would cap out about ~125MB/s or so (depends on the quality of the NIC, switch, and other factors, of course).

As for the Celeron, if you get a decent hardware-level controller card, that should pretty much be a non-issue, since hardware-based RAID is regulated by the controller, which has its own built in processor and memory to do parity calculations.

i was either going to go with raid 1 or raid 5. also, i was wondering how much of a performance loss i would take if i went with a celeron instead of a hardware based controller.

[Syntax Error]

i was either going to go with raid 1 or raid 5. also, i was wondering how much of a performance loss i would take if i went with a celeron instead of a hardware based controller.

Well, I'm assuming your NAS isn't really accessed as you, the user, for general computer applications, but acts as what it is, as a storage device. Regardless of the CPU load on RAID 5 parity write, it shouldn't really matter to you if it's on a secondary computer that you mainly do not use on a day-to-day basis. Your mileage may vary depending on your operating conditions, operating system, and other factors (such as the drives you use in the array, whether or not if they are homogenous in drives [same drives, same models, same manufacturers, same in design]).

[Lazn_Work]

FYI: with software RAID, RAID 1 will be much faster in writes than RAID 5. Reads will be somewhat faster with RAID 5 but don't expect a huge increase. So keep that in mind if you are looking for RAID 5 as a performance enhancer.