ZFS vs hardware RAID for low power file server

You may want to read through this thread:
http://www.tomshardware.co.uk/foru [...] _14_0.html

Don't use hardware RAID if you want to use ZFS - you'll lose one of the most important benefits of ZFS - the self healing process. Software RAID in these cases is clearly superior to hardware RAID.

Hi sub mesa,

Thanks for all the helpful info. There's loads to get through...!

I'll make sure I only consider 64-bit architectures. I assume there's a trade-off between CPU power consumption and controller power consumption when considering ZFS vs hardware driven RAID. IOW, I'm assuming that:
- ZFS solution = gruntier CPU = more watts, but controller consumes less power;
- Hardware RAID = weedy CPU = less watts, but controller consumes more power;

Is that right? Do you know which will be more efficient in terms of power consumption?

Will a chip like the Via Nano be heavy-duty enough to run, say, FreeNAS and ZFS or OpenSolaris and ZFS?

Cheers - Adam...

Low-power means something like 35-50W excluding disks. This is easily achieveable with an AMD setup and efficient power supply.

For example:

• AMD Dualcore with 35W or 45W tdp means ~2-3W idle
• AMD 740G/780G/785G chipset means ~2W idle
• Amacrox 400W fanless PSU is 90%+ efficient, one of the most power efficient power supplies and comes without a fan

If you go for 2,5" HDDs you can even go for an "extreme" setup with PicoPSU power supply, which is like ~97% efficient and can reduce idle power consumption to 30-35W, while still providing high performance with lots of memory and dualcore chip to saturate your gigabit NIC.

Note that TDP can be misleading; while the maximum power consumption is important for chosing the correct power supply, its not important for actual power consumption, as your hardware will idle most of the time. In fact, all PCs in the world idle more than 90% of the time. Idle power consumption is what you should look at if you are concerned with the environment and/or want to save on energy costs.

There are more reasons why you would want 64-bit CPU for ZFS. This advanced filesystem is simply not stable on 32-bit systems, due to a maximum of 1GB kernel memory. In many cases with heavy disk I/O, ZFS would cause the operating system to crash with a "panic: kmem_map too small" message. Its possible to tune ZFS heavily so it runs reasonably stable on 32-bit, but that would mean disabling lots of stuff that decrease performance.

32-bit is limited to 2GB per process; its Windows that uses up to 3GB and 1GB kernel memory for 4GB memory systems. With PAE you can have like 64GB RAM on 32-bit systems, but the 2GB-per-process still applies, unless the process/application is specially compiled which is extremely rare. Performance with PAE would be affected too. You really want to have a 64-bit system in this case.

@HappyBison, what kind of ZFS setup do you run and are you happy with the setup?

Good to hear others are running FreeBSD as well. Are you running 7-STABLE or 8.0?

I haven't compared FreeBSD ZFS performance directly to OpenSolaris yet, if you would have any benches i would be very interested in them.