http://www.newegg.com/Product/Product.aspx?nm_mc=AFC-SlickDeals&cm_mmc=AFC-SlickDeals-_-NA-_-NA-_-NA&Item=N82E16817151088&Tpk=N82E16817151088

 

Coupon - PSU982

 

 

Drool.  I wish Newegg posted better specs about Seasonic PSUs.  "Ample +12V Output".  Thanks...real helpful.

 

The picture shows that it is actually 54A on the +12V rail.  That should do.

Do for 20 drives? I'm trying to decide whether to replace my Corsair 850 beast...

Yes, it will definitely work for 20 green drives.  20 green drives should require 40A.  20 7200 rpm drives should require around 60A, so it isn't enough for that.  A mixture of the two should be fine as long as you have half or more green drives.

Startup current for popular unRAID hard disks

 

Information taken from the following:

 

http://www.xbitlabs.com/articles/storage/display/15-2tb-hdd-roundup_18.html#sect0

http://www.xbitlabs.com/articles/storage/display/2tb-7200rpm_18.html#sect0

http://www.xbitlabs.com/articles/storage/display/1tb-2tb-roundup-2_16.html#sect0

 

 

Start current for 12 volts

 

5400-5900 rpm

2TB WD Green 1.41 or 1.51

2TB Samsung F3 1.46

2TB Seagate LP 2.34

 

7200 rpm

2TB WD Black 1.60

2TB Hitachi 7K2000 1.91

2TB Seagate XT 2.39

 

Drive manufacturer has more to do with current requirements than rpm. The 2 amp per drive is a good rule of thumb no matter the drive speed.

Now this is all from what I read, so it might not be completely accurate, but ... Don't forget to figure in PSU aging that has detrimental affects on it's ability to deliver power as the years go on. If that's the case, I'd say the rule of thumb of 2 Amps WD/Hitachi/Samsung and then 3 Amps for Seagate to be able to still use the PSU in 3 years.

 

Can anyone add additional insight into that realm?

The primary components in a power supply that would degrade due to age are the capacitors. The factors that would help accelerate the aging are heat and load. Quality capacitors in a conservative design should fare well. UnRAID is very gentle on power supplies. Only during simultaneous disk starts is the maximum capability of the power supply approached. Most of the time the power supply is loafing at 10 to 20 percent of capacity.

 

I trust Seasonic. They warranty the X650 for 5 years and the Corsair 650TX (Seasonic made) also carries a 5 year warranty. I expect both will last that long. Unfortunately I don't have the equipment to perform a load test to see of my 5+ year old Seasonics can still meet load specifications. Interesting topic, do you have data to point to?

A load test will not tell you much.  The capacitors age will eventually cause them to have a higher equivalent-series-resistance.

 

Once they have a high ESR, they stop being able to filter noise on the power supply bus.  That will show itself a random errors, in just about anything sensitive to a poorly filtered power supply.  (disks, memory, CPU... just about anything that does not subsequently filter the supply to its components.)

 

A "load" test usually is a simply as seeing if the voltage can be supplied at the rated current.  That, unfortunatly, is not enough to know the supply is working properly.  In fact, no "static" test will.  You must put the supply under a dynamic load (one constantly changing) to see if it can filter out the resulting noise.  A parity check is one such dynamic load, as is the spin-up of multiple drives while serving media on another.

 

All you can do is hope the manufacturer used capacitors rated for 100C rather than 80C, and long life rather than short.  Those better capacitors equate to more expense, so shop these types of sales and try to get a name brand at some discount if you can.