RAID-Z2, Cost/Disk/Reliability Comparison

[Faluzure]

Last question (for now)... I promise!

So I've planned out my system, chose a case and everything. Now it comes to the drives. I plan on using RAID-Z2 for my setup and the optimum configuration within my price range is either 4 or 6 drives.

With that said... I made a nice chart, based on current pricing.
WD Red 4TB - $169.99
WD Red 3TB - $120.99
WD Red 2TB - $98
WD Red 1TB - $69.99

HDD Size (TB) // 6 Drive Cost // Avail Space // 4 Drive Cost // Avail Space
4................$1,019.94.......16.............$679.96.........8
3................$725.94.........12.............$483.96.........6
2................$588.00.........8..............$392.00.........4
1................$419.94.........4..............$279.96.........2

I'm looking at the 8TB "free space" configuration, which is available in the chart for both 6 drive & 4 drive arrangements.

Off the bat, I can see if I went with the 6 x 2TB arrangement, it would:
* Occupy 2 extra drive bays, limiting expandability.
* Increase power consumption by 2 drives
* Increase failure rate by 2 drives.

Other than the positive of saving $100, is there any other positive to choosing the 6 x 2TB drive arrangement?

Thanks in advance.

 

[Faluzure]

Anyone?

 

[Starpulkka]

Damn. i bite thenn. So if you are looking near 8TB usable space you can have 8.2TB 5x 3TB drives at 605$ as price will be very same what you planned on 6x 2tb drives 588$ but remember you really cant fill it 100% as pool will lock itself

Code:

4tb 5x 10.9TB 850$
4tb 4x 7.3TB  680$
2tb 6x 7.3TB  588$
3tb 5x 8.2TB 605$
3tb 6x 10.9TB 726$

or something like that

Ofcourse i would recommend raidz2 3tb 6x 10.9TB 726$ (as you cant fill pool 100% 8TB is nearly over sweet area in that 6x 3TB raidz2 setup) also look look page 2 raidz2 https://docs.google.com/a/delphix.c...TjHv6CGVElrPqTA0w_ZY/edit?pli=1#gid=930519344

 

[mjws00]

Heh. I almost answered this one for ya. But there are a LOT of threads addressing this issue and the only way to "do it right" is to write a paper.

Here are the cliff notes:

1. Consider the raw costs of space per TB or GB. i.e your 1TB drive is $69.99/TB the 4TB drive is $42.50/TB (so 4TB drive wins)
2. The count of spindles matters. Both in terms of redundancy and performance. More spindles = More potential speed both in terms of throughput and IOPs. However, on 1Gbe we are saturated instantly for throughput. So often this doesn't matter at home.
3. It is often easier to put the larger drives in, as it increases over all capacity of the box for future use.
4. Starpulkka did some math for you on Usable SPACE. That you want to look at again in terms of $/TB, parity levels, performance.

Good luck. (Starpulkka hit enter while I was typing.)

 

[Faluzure]

Thanks guys.