Vdev size options in new setup

[Kevin Horton]

I'm looking for advice on how many drives I should start with on the FreeNAS box I will build. I'll use a Fractal-Design Node 804 case which could hold up to 10 drives. I currently own 4 x 4TB WD Red drives that are running in a Synology NAS that will be replaced by the FreeNAS box. I'll back up the data, then put those drives in the FreeNAS box.

I will be using RAIDz2. I only need about 5TB usable storage now, but that will increase with time, and I hope to be able to use this setup for five or more years, with increases in storage capacity as needed.

Options I'm considering:

1. Buy six more drives now, and run them in 8+2. That implies that any future storage expansion would be by buying 10 drives, which would be a lot of money to digest at once. The 8+2 would hopefully maximize storage efficiency, if I am not using data compression.

2. Buy one more drive now, and run them in 3+2. I'd buy five more drives when I need to expand, and set up a second vdev. The next expansion would be by replacing the drives in the original vdev with larger capacity ones. I'd be sacrificing storage efficiency unless I used data compression, and I would always be losing 4 drives to parity, with only six data drives.

I'm leaning towards option 2, but I'd love to learn what I haven't considered.

Thanks.

 

[Fuganater]

Option 1 if you can manage the money now.
Option 2 if you can't.

Either way, both would be good but Option 2 gives you more redundancy.

 

[danb35]

Whether you go with option 1 or 2 (and I'd likewise vote for 1 if you can possibly swing it), you will be using compression unless you affirmatively disable it--it's enabled by default, and it would be a rare case that would call for disabling it.

 

[DrKK]

Whether you go with option 1 or 2 (and I'd likewise vote for 1 if you can possibly swing it), you will be using compression unless you affirmatively disable it--it's enabled by default, and it would be a rare case that would call for disabling it.

I've actually disabled it. 99% of my stuff is music/movies, so it's pointless really for me

 

[Robert Trevellyan]

Option 2 looks good to me, for the reasons you state. If you don't need 10 drives now, why shell out at 2015 prices? By the time you have more than 5TB of data, who knows what will have changed?

 

[Bidule0hm]

I've actually disabled it. 99% of my stuff is music/movies, so it's pointless really for me

With compression enabled you're basically trading CPU resources for free space and very often you'll have more than enough CPU resources (when is the last time your CPU hit 100 % usage on your NAS?...) so compression is basically free and there's no real reason to disabled it usually.

 

[Kevin Horton]

How powerful a CPU does it take to be able to use compression without having it limit performance? I want to be sure I don't under spec the CPU for the box I will build in January.

 

[Bidule0hm]

Not much, a scrub is more CPU intensive than a copy. I have a i3 4360 and I never saw it going over 25 % usage.

 

[DrKK]

You're absolutely right. There would be no noticeable CPU impact if I were using compression. Still, no real benefit either. I guess I just disabled it on the main pool for principle. The jail pool (which is separate, on SSD), does have it enabled.

 

[Kevin Horton]

Thanks for the input guys. I'll go with option two. I could afford option one, but I'd rather reserve that money for building another aircraft.

 

[Robert Trevellyan]

How powerful a CPU does it take to be able to use compression without having it limit performance?

Not powerful at all, using LZ4, which is the default.

LZ4 is lossless compression algorithm, providing compression speed at 400 MB/s per core (0.16 Bytes/cycle). It features an extremely fast decoder, with speed in multiple GB/s per core (0.71 Bytes/cycle).

In other words, a single core of a modern CPU can compress fast enough not to bottleneck a gigabit network connection, and decompress fast enough to saturate a 10 gigabit network connection.

 

[Ericloewe]

Not powerful at all, using LZ4, which is the default.

In other words, a single core of a modern CPU can compress fast enough not to bottleneck a gigabit network connection, and decompress fast enough to saturate a 10 gigabit network connection.

On compressible workloads, compression actually makes the system faster by reducing the disk bottleneck. Assuming there's no network in the mix, of course, since that's the real bottleneck.

 

[Kevin Horton]

Not powerful at all, using LZ4, which is the default.

In other words, a single core of a modern CPU can compress fast enough not to bottleneck a gigabit network connection, and decompress fast enough to saturate a 10 gigabit network connection.

I'm planning on using an Intel Pentium G3258, as I don't currently plan to run anything on the NAS except FreeNAS. It is relatively modern (Haswell), dual core at 3.2GHz, compatible with EEC RAM. It is popular among the enthusiast crowd, as it is unlocked, so it should be easy to sell later if I need to upgrade to a faster CPU.

 

[DrKK]

It is popular among the enthusiast crowd,

Just out of curiosity, what did you think *we* were?

We're quite familiar with every single 1150-socket SKU, sir, down to detailed specifications on esoterica. :)

 

[Kevin Horton]

Just out of curiosity, what did you think *we* were?

We're quite familiar with every single 1150-socket SKU, sir, down to detailed specifications on esoterica. :)

Hmm. I haven't been hanging around here long enough to really figure out who the core FreeNAS forum members are. It looks like a fairly diverse bunch, as near as I can tell from a few weeks of lurking, and one week of posting. I certainly wouldn't call myself a "PC enthusiast", although I have been using the CLI on OS X for over 10 years, and have written quite a few scripts for my own use.

I'm looking forward to getting going with the FreeNAS box in the new year. I've just downloaded VirtualBox so I can play around with FreeNAS, before I buy real HW.

 

[Robert Trevellyan]

I'm planning on using an Intel Pentium G3258, as I don't currently plan to run anything on the NAS except FreeNAS ... it should be easy to sell later if I need to upgrade to a faster CPU.

I've been running a G3220 for a few months now (with plenty of RAM). Trust me, you won't need to upgrade your CPU.

I've just downloaded VirtualBox so I can play around with FreeNAS, before I buy real HW.

:D