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How to measure the drive spin-up peak current

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danb35

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Other method with an oscilloscope (or a DMM with fast peak hold): buy a clamp-on current probe like this one for about $50 US. It runs on a 9V battery, clamps over the wire you want to measure current on, and converts the current into a voltage. The model I ordered has two switch-selectable ranges, 1 mV / 10 mA and 1 mV / 100 mA. If you then set your probe multiplier to 10x or 100x respectively, you can directly read the current from the screen.

Advantages: You don't have to build anything, or cut any wires in your drive wiring. If you set up your scope correctly, you can directly read current on your screen. Because it clamps over any single wire, you can easily measure the particular rail you're interested in. It's completely isolated from your server, so no chance of shorting anything out on the scope or the server.

Disadvantages: It's $50--3x the price of @Bidule0hm's solution, and that assumes you've already got a 'scope. And that's a cheap one from China--brand names are hundreds of dollars. It has a bandwidth limit, though this one's stated at 30 KHz, so it shouldn't be a problem here.

I've ordered one, thinking it will be interesting to see how well it works. I'll post a few traces when it comes in.
 
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Bidule0hm

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Great idea, I'll add that asap ;)

It's a shame we need to measure a DC current, because if it was AC only it's super easy to make a current transformer (basically what's in a AC clamp current meter...).

Edit: added the current clamp method in the OP.
 
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Ericloewe

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I still think that in many cases it'll average out, but, boy, that's actually a little scarier than I thought it was, AND I'M SUPPOSEDLY THE PARANOID ONE.
Indeed, those margins given by the datasheets don't seem to be there to account for product variances as much as they are to make the drives look better on paper...
 

solarisguy

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A question to those who started measuring real life startup currents.

In January of 2009, WD has released the following utility for their Green Power drives:
WDSpinUp Utility (WDSpinup version 1.00 for DOS)
http://support.wdc.com/downloads.aspx?p=114
http://support.wdc.com/downloads.aspx?p=114&lang=de
http://support.wdc.com/downloads.aspx?p=114&lang=en
http://support.wdc.com/downloads.aspx?p=114&lang=fr

From wdspinup.txt
Code:
DESCRIPTION
- DOS Level utility to configure the low current spinup feature for Western
  Digital GreenPower(TM) drives.
- Allows spinup current to be configured to low or super low.
- Reports spinup current setting (low or super low).


FEATURES
- Scan for all drives. Non-WD Drives shall only show the model number and
  serial number.
- Unsupported disk drives will report 'This drive does not support dual spinup
  current modes.'
- Uses a Vendor Specific Command to get or set the spinup current setting.
Has anyone played with that setting?
 

GrumpyBear

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Bah, you're not the paranoid one if you don't have a RAID-Z3 with only 8 drives... :D

Yep, I'd love to know too. If I had the money I'd do a ton of experiments (starting with the good old "whats is the limit (how many times per day) to spinning up/down the drives for saving some drive life") but yeah, all I can do for now is doing a fair comparison between the WD Red and Seagate NAS (that's why I have 4 of each).
Nice work on measuring the PS inrush from the disks.

BTW fellow paranoid. One of my Seagates have crapped out and while I have successfully traversed the wonderfully obtuse RMA forms I have picked up another 3TB WD to replace it with and will keep the RMA'ed Seagate as a spare once I burn it in and validate it.
 

Bidule0hm

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Indeed, those margins given by the datasheets don't seem to be there to account for product variances as much as they are to make the drives look better on paper...
Actually it's the first time I see a datasheet lying. The next time I open the server I'll take the captures for the ST3000VN000 and WD30EFRX ones to see if they are lying on thoses too (plus it'll be useful data for everyone because it some of the drives we use the most here).

@solarisguy Thanks ;)

Didn't know about WDSpinUp, sounds interesting.

@GrumpyBear Thanks ;)

RMA'ed one of the 3 TB Seagate a few weeks ago too and received a 4 TB one (badblocks is still running on it, 57.2 % after 90 hours, it's slooowwwww...), it's the one I used for the capture in the OP. WD drives win for now (and they are quieter) :)
 

Bidule0hm

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I added the captures for the Seagate NAS 3TB [ST3000VN000] and the Western Digital Red 3TB [WD30EFRX] ;)
 

Ericloewe

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So that Red is really hitting the 30W (assuming 5V current is low) number I've been spreading for ages now, which I'd arrived at by conservatively looking at the datasheet and saying "Yeah, this is nicely below 30W". Not a good sign.

What's the date of manufacture on that Red, by the way?
 

Bidule0hm

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I didn't write it and it seems I can't see it with smartctl so all I can say it's that the drive is from 2014, I hope it's precise enough for you :)
 

solarisguy

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I didn't write it and it seems I can't see it with smartctl so all I can say it's that the drive is from 2014, I hope it's precise enough for you :)
You can try to use its serial number on the Western Digital warranty page, since in many countries warranty starts from the day the drive was manufactured...
 

solarisguy

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So that Red is really hitting the 30W (assuming 5V current is low) number I've been spreading for ages now, which I'd arrived at by conservatively looking at the datasheet and saying "Yeah, this is nicely below 30W". Not a good sign. [...]
I was scared of that initial 30W (WD specs suggest 25W), so I told the HBA to start my 8 drives one by one.
 

Bidule0hm

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Yeah, but I have 4 Reds and 2 are older than the other 2 (I started with 4 drives in RAID-Z2 and then switched to 8 drives in RAID-Z3 after that) so I can give two dates but I still doesn't know which is the right one :P
 

Ericloewe

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For my purposes, a vague "2014" goes a long way. It's mostly about keeping track of the various versions and revisions, to see if anything unusual pops up.
 

Bidule0hm

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I can put some info on the FW and co if it can be useful:

Code:
Model Family:     Western Digital Red
Device Model:     WDC WD30EFRX-68AX9N0
Firmware Version: 80.00A80
User Capacity:    3,000,592,982,016 bytes [3.00 TB]
Sector Sizes:     512 bytes logical, 4096 bytes physical
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   ACS-2 (minor revision not indicated)
SATA Version is:  SATA 3.0, 6.0 Gb/s (current: 6.0 Gb/s)
Local Time is:    Sat Nov  7 01:07:03 2015 CET
SMART support is: Available - device has SMART capability.
SMART support is: Enabled


Code:
Model Family:     Western Digital Red
Device Model:     WDC WD30EFRX-68EUZN0
Firmware Version: 82.00A82
User Capacity:    3,000,592,982,016 bytes [3.00 TB]
Sector Sizes:     512 bytes logical, 4096 bytes physical
Rotation Rate:    5400 rpm
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   ACS-2 (minor revision not indicated)
SATA Version is:  SATA 3.0, 6.0 Gb/s (current: 6.0 Gb/s)
Local Time is:    Sat Nov  7 01:07:07 2015 CET
SMART support is: Available - device has SMART capability.
SMART support is: Enabled
 
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Ericloewe

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I can put some info on the FW and co if it can be useful:

Code:
Model Family:     Western Digital Red
Device Model:     WDC WD30EFRX-68AX9N0
Firmware Version: 80.00A80
User Capacity:    3,000,592,982,016 bytes [3.00 TB]
Sector Sizes:     512 bytes logical, 4096 bytes physical
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   ACS-2 (minor revision not indicated)
SATA Version is:  SATA 3.0, 6.0 Gb/s (current: 6.0 Gb/s)
Local Time is:    Sat Nov  7 01:07:03 2015 CET
SMART support is: Available - device has SMART capability.
SMART support is: Enabled


Code:
Model Family:     Western Digital Red
Device Model:     WDC WD30EFRX-68EUZN0
Firmware Version: 82.00A82
User Capacity:    3,000,592,982,016 bytes [3.00 TB]
Sector Sizes:     512 bytes logical, 4096 bytes physical
Rotation Rate:    5400 rpm
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   ACS-2 (minor revision not indicated)
SATA Version is:  SATA 3.0, 6.0 Gb/s (current: 6.0 Gb/s)
Local Time is:    Sat Nov  7 01:07:07 2015 CET
SMART support is: Available - device has SMART capability.
SMART support is: Enabled
Which one of them did you test?

Mine are all 68EUZN0:
Code:
=== START OF INFORMATION SECTION ===
Model Family:     Western Digital Red
Device Model:     WDC WD30EFRX-68EUZN0
LU WWN Device Id: 5 0014ee 25f7354fe
Firmware Version: 80.00A80
User Capacity:    3,000,592,982,016 bytes [3.00 TB]
Sector Sizes:     512 bytes logical, 4096 bytes physical
Rotation Rate:    5400 rpm
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   ACS-2 (minor revision not indicated)
SATA Version is:  SATA 3.0, 6.0 Gb/s (current: 6.0 Gb/s)
Local Time is:    Sat Nov  7 23:09:15 2015 WET
SMART support is: Available - device has SMART capability.
SMART support is: Enabled
 

Bidule0hm

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I don't know, you'll have to wait the next time I open the server :P
 

danb35

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My current clamp came in yesterday, so I checked a few drives with it this morning.

Here's a trace from Seagate Barracuda ST2000DM001, 7200 rpm 2 TB:
DS2_QuickPrint1.png


Here's one from a WD Green WD20EARX-008FB0 2 TB
DS2_QuickPrint2.png


and here's one from a WD Red WD30EFRX-68EUZN0 3TB
DS2_QuickPrint3.png
 

Bidule0hm

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Nice, but there's a problem: the values are too low.

It's the +12 V current or the total current?

Are you sure the probe is correctly calibrated? (checked with a known continuous current load?)

Are you sure you haven't done any mistake in setting the probe att ratio in the scope? (seems like an error of roughly a factor of 2)
 

danb35

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That is only the +12V current. I have not checked it against a known load, largely because I don't have one. The scope is set to a 10x probe, which should be correct--this unit was set to 1 mV / 10 mA.
 
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