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I d like to share a weird thing I came across with the above aforementioned disk. I have two of these

WDC WD40PURZ-85AKKY0
WDC WD40PURZ-85TTDY0

both are purple 4tb drives. Before use them in an array (along with other 4tb drives) I wanted to check the drives and started with most simple one to check the attributes of the drives with smartctl -i /devsd(whatever letter is being recognised) and I noticed that from the

WDC WD40PURZ-85AKKY0 specs
Model Family: Western Digital Purple
Device Model: WDC WD40PURZ-85AKKY0
Firmware Version: 80.00A80
User Capacity: 4,000,787,030,016 bytes [4.00 TB]
Sector Sizes: 512 bytes logical, 4096 bytes physical
Rotation Rate: 5400 rpm
Form Factor: 3.5 inches
Device is: In smartctl database [for details use: -P show]
ATA Version is: ACS-3 T13/2161-D revision 5
SATA Version is: SATA 3.1, 6.0 Gb/s (current: 6.0 Gb/s)
Local Time is: Fri Jan 15 01:37:42 2021 EET
SMART support is: Available - device has SMART capability.
SMART support is: Enabled
capabilities: (0x11) SMART execute Offline immediate.
No Auto Offline data collection support
Suspend Offline collection upon new command.
No Offline surface scan supported.
Self-test supported.
No Conveyance Self-test supported.
No Selective Self-test supported.
SMART capabilities: (0x0003) Saves SMART data before entering
power-saving mode.
Supports SMART auto save timer.
Error logging capability: (0x01) Error logging supported.
General Purpose Logging supported.

Notice the 4 No’s referring to

No Auto Offline data collection support.
No Offline surface scan supported.
No Conveyance Self-test supported.
No Selective Self-test supported

While the other drive WDC WD40PURZ-85TTDY0 exact same model - same firmware has them as supported according to this

Model Family: Western Digital Purple
Device Model: WDC WD40PURZ-85TTDY0
Firmware Version: 80.00A80
User Capacity: 4,000,787,030,016 bytes [4.00 TB]
Sector Sizes: 512 bytes logical, 4096 bytes physical
Rotation Rate: 5400 rpm
Form Factor: 3.5 inches
Device is: In smartctl database [for details use: -P show]
ATA Version is: ACS-3 T13/2161-D revision 5
SATA Version is: SATA 3.1, 6.0 Gb/s (current: 6.0 Gb/s)
SMART support is: Available - device has SMART capability.
SMART support is: Enabled
capabilities: (0x7b) SMART execute Offline immediate.
Auto Offline data collection on/off support.
Suspend Offline collection upon new command.
Offline surface scan supported.
Self-test supported.
Conveyance Self-test supported.
Selective Self-test supported.
SMART capabilities: (0x0003) Saves SMART data before entering
power-saving mode.
Supports SMART auto save timer.
Error logging capability: (0x01) Error logging supported.
General Purpose Logging supported.

How can that be? Are these attributes

Auto Offline data collection support.

Offline surface scan supported.

Conveyance Self-test supported.

Selective Self-test supported

enabled-disabled from the underlying OS or with smartctl commands?

After that I also checked 2 skyhawk devices also 4tb and asked some friends of mine with purple ones and all supported those 4 attributes.

Do you have any idea what is happening here?

PS I ve had the useless idea of posting that on official wd forum but that forum it seems dead long time ago.

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1 Answer 1

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WD Purples are surveillance-specific drives, so I don't expect them to export detailed SMART stats. You have two different driver models/revisions (85AKKY0 vs 85TTDY0), so the former probably exports less SMART attributes/capabilities.

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  • Thank you for your quick answer. So what you mean is that these 4 attributes are not important or that it might be supported but not shown in the smartctl stats
    – ieronymous
    Jan 17, 2021 at 19:28
  • 1
    Not supporting (or exposing) such attributes will not impair drive performance in any manner, but some tests (ie: selective surface scan) will not be available. Moreover, the missing automatic offline data collection can somewhat impair drive health monitoring. If used in an important server, I would replace it (if possible).
    – shodanshok
    Jan 17, 2021 at 21:25
  • Thank you I ll keep that in mind .... One last thing....do you thing that this command sudo smartctl --offlineauto=off /dev/sd(whatever) should be run to each disk that is going to be used in a nas environment? It turns off the abiliiy of the drive to auto-check itself every (I cant remember now the time limit which degrades the performance a lot quicker)
    – ieronymous
    Jan 17, 2021 at 23:02
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    @ieronymous "Offline" checks run only when the disk is idle, so they should have very little impact on performance. Jan 18, 2021 at 0:54

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