SD card durability: Industrial SLC NAND SD cards?

I’ve ordered a few to start a long term test and I’ve added an option to the emonPi / emonBase to optionally specify a WD SLC NAND SD card.

I’ll report back in hopefully 5-10yrs :grinning:

Thanks for your help.


I have been running a micron SD card for the last year. we have had a few power outages and no problem so far. th P/N is: MTSD064AHC6MS-1WT

In the trade I paid £11+vat

I still this having an option of a USB stick with nightly / weekly automated backups would be nice.

Dated June of 2018, so not current, but some good info nonetheless.

I’ve been told that with solid state drives, the controller writes to different areas to prevent specific areas from being written to too often. The result is that if the SSD size is doubled, for the same software, each segment is written to half as often. The expected life (or time before serious degrade) is therefore doubled (or at least increased).

Would the same effect be noticed on an SD card, and would it therefore be a strategy to oversize the SD card?

Perhaps Glyn you can let us know in 10-20 years? :slight_smile:

What you’re describing is termed wear leveling.
SD cards with wear leveling are now fairly common.

If the card has WL, then the answer to both questions is yes.

Info on Western Digital Purple SD cards:

From the link shown above:

Designed and tested to withstand 24/7 continuous write workloads, meet data retention requirements, and accommodate harsh environmental conditions, the industrial SD and microSD cards and WD Purple microSD cards are ideal for low footprint, local storage at the surveillance edge, working in concert with other Western Digital solutions in on-premises DVRs and NVRs, in near-edge cloud servers and in back-end cloud data centers.

12 USD for a 64 GB µSD card.

Sounds like this puppy is just the ticket. Price is £18.49 for a 64 GB µSD card.
UK supplier:

Some interesting info on wear leveling:

Thank you. I assume the wear levelling algorithm runs directly on the SD card itself, and not on an external (i.e. on the Pi) controller?

(Which means the WD SD card is so much more than just 512 billion on/off switches)

I note also the WD SD card on Amazon makes no mention of wear levelling - so buyers may need to dig deeper. More discussion here:
Read/Write cycles of a SD card - Raspberry Pi Forums (which also answers my question above)


The card on the Amazon page is the WD Purple, which does employ wear leveling.
That’s why I posted the link to WD’s product info page.

On that page:
Advanced firmware memory management features, including power immunity, auto/manual refresh, ECC, and wear-leveling

Ordered one and will give it a try, not having much luck with my ordinary Sandisk sd card right now…

Was cheaper from Western Digital themselves than Amazon (but watch out for £6 postage on top).

Below is a link to a thread on the Raspberry Pi Forum, providing an app that can read out the current ‘health’ status data for two Industrial class microSD cards: those from SanDisk / WD, and those from Apacer and offshoots.

This allows say weekly monitoring this status (equivalent to on an SSD comparing TBW to rated max TBW). To track that the device does not exceed lifetime limits.


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The Meteobridge weather station software/weather data server for RPi can only be used with a limited range of industrial SLC cards, as stated on following link.


re: Meteobridge limited range of industrial SLC cards

That list does include both the cards supported by the Raspberry Pi microSD ‘health check’ app (‘sdmon.c’): SanDisk/WD and Apacer. Both types of NAND cells: SLC and MLC.

My impression is that WITH all of the extensive robustness features of the SanDisk Industrial cards (ECC, wear leveling, read disturbance correction, powerfail protection, etc.) – that MLC is now on par with the range of endurances offered by SLC. At a fraction of the cost. See the SanDisk / WD doc, with listed TBW figures:

I agree, we’re now using industrial grade SD cards as standard in all OpenEnergyMonitor units. We’re currently using SanDisk SDSDQAF3-016G-I

It would be very interesting if we could read the health status of this card!

Glyn, hi.

I have this same type of SanDisk Industrial card, and the ‘sdmon.c’ previously mentioned program DOES read out the health status. See the Pi Forum link I mentioned previously to download the zip file containing sdmon.c and the Makefile.

Regards, William

Ah that’s cool!

I’ve just tested for myself, the pre-compiled release gave lots of errors, so I compiled it. I’m now getting less errors but no reading

git clone
cd sdmon/src

I’ve tried with and without the -s parameter. Any idea what I’m missing?

[email protected]:~/sdmon/src $ sudo ./sdmon  /dev/mmcblk0
"version": "",
"date": "2022-04-08T02:29:52.000Z",
"idata.response[]":"0x900 0x00 0x00 0x00",
"error2":"2nd CMD56 CALL FAILED: Connection timed out"
[email protected]:~/sdmon/src $ sudo ./sdmon -s  /dev/mmcblk0
"version": "",
"date": "2022-04-08T02:30:34.000Z",
"usage":"wrong argument count"

Glyn, hi.

Ognian has not yet incorporated the SanDisk mods. That is why I posted my zip on the Pi Forum thread. It might take him some days or a week or so to merge my mods. His current version does not understand the ‘-s’ or ‘-a’ switches.

Just download my zip and build that, then “sudo ./sdmon -s /dev/mmcblk0”


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The sdmon.c may also assume you are running a 64 bit Pi OS. That’s what I have here. Have not tested on 32 bit Pi OS. If you have 32 bit and it works ok, let me know. All the #includes should account for this automatically…

I’ve just tested your version of sdmon from the RasPi forums on my an emonPi with 32-bit Raspberry Pi OS, and it worked!

"version": "0.01",
"date": "2022-04-12T14:50:32.000Z",
"manufactureYYMMDD": "210712�|���R��������T��p���",
"healthStatusPercentUsed": 1,
"featureRevision": "0x1f",
"generationIdentifier": 5,
"productString": "SanDisk                     ",

I’ll await these changes to be built into the Ognian git repo, then look at a way we can get this info displayed on the admin panel in Emoncms on the emonPi.

Glyn, hi. Just sent you an email.

The zip posted on the Pi Forum has been updated to fix the minor string termination glitch you saw. As far as I know Ognian is still in progress on the merge to his Github repo.

Regards, William

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