Choosing the right setup.

[JWMutant]

Afternoon peoples.

 

As this is my first custom built NAS and my first time using unraid I want to pick peoples brain on setting up the correct drives in the correct config.

 

What is listed is the drives I have and understand these are purely drives I have sitting around.

 

1 x 3TB Seagate NAS Drive (5900rpm) running on SATA 2 off the motherboard. This is currently my Parity Drive.

4 x 3TB WD Red Drives (Drive speed unknown, however due to intellipower these are more than likely 5900rpm) These 4 drives are running on my IMB SAS controller at full SATA 3 speed.

1 x 3TB Seagate Barracuda Drive (7200rpm) this drive is running on my IMB SAS controller at full SATA 3 speed.

3 x 2TB Seagate Barracuda Green Drives (5900rpm) These 2 drives are running on my IMB SAS controller at full SATA 3 speed.

 

Lastly I have a 240GB SSD I am using as my cache drive running at SATA 3 off the motherboard.

 

Ideally I would like all drive to at least be spinning at the same speed which would mean buying a few new drives. There is one limitation I have in that the motherboard has 6 SATA ports but only one of them is SATA 3, which is why I bought a 2 port SAS controller.

 

Once again understand that this NAS is purely made out of spare parts I had sitting around the house, except for the SAS controller.

 

I would think that if I had to choose 1 drive above all to be SATA 2 it would be the parity drive. From what I understand of the parity drive it will only be as quick as the slowest data drive.

 

As you can see from the image, I am limited as to what cards I can add and getting SAS controller with more channels at this point in time is something I would like to avoid.

[tdallen]

The general rule of thumb is for the parity drive to be as large as, and as fast as, any other drive in the array.  Array operations don't necessarily access all HDs, so you don't want operations against a fast disk slowed by a slow parity drive.  That said, spinning hard disks typically can't saturate SATA 2 (forget about SATA 3) and I find that in my older system the motherboard SATA 2 ports are actually 10-15% faster than my add-in SATA 3 controller.  YMMV, of course.

 

Bottom line, your SSD cache drive definitely belongs on a SATA 3 port.  In theory your best setup would be for parity to be 7200rpm on a SATA 3 port, but I don't think you're really going to see hugely meaningful differences in array operation speed whether the parity drive is 5900 or 7200 RPM, or on a SATA2 or SATA3 port.  The thing that has had the most impact for my array was moving a 6TB parity drive and adding a 6TB data drive - the higher areal density of those drives make them about 25% faster than my 3TB drives.  To go along with that, my painfully old 250GB 7200rpn spinning cache drive  is on a SATA 3 port and is by far the slowest drive in my system.

 

You might want to check out jbartlett's diskspeed.sh - it's a great little utility that will benchmark your HD speeds.