Failing: Sandisk Ultra microSDXC 128Gb (Class 10, UHS-I, Up to 80MB/s)

The new year just keeps getting better. Sure, the battery in the phone is failing, but the microSDXC card as well?!

The Culprit

The culprit was a Sandisk Ultra microSDXC card of 128Gb capacity, Class 10, UHS-I rated up to 80MB/s. This is not the same card that I previously reviewed, but a newer version of that card that I bought when I purchased my Xiaomi Redmi Note 2. As 128Gb cards (at the time) were not widely available from different manufacturers, and compatibility was problematic for some, I stuck with Sandisk. As I’m aware of the catastrophic consequences of fake flash, I purchased the card from a reputable local seller which sells local stock.

The card was purchased on the 4th February 2016, less than a year ago. To see it run into trouble is rather unexpected.

The Symptoms

The first sign of troubles came about two months ago, when I realized that some photos I took on my Redmi Note 2 came up as “Load Failed!” in Quickpic. It was only one photo, so I dismissed it as probably a glitch such as an interface bus issue – maybe something like a sparking pantograph on a passing train during the photo recording process might have disrupted it.

Later on, it affected three photos in a row sequentially while I was at the conference in Canberra. I thought “gee, something must be wrong with the software” and dismissed it again.

It was only until last week, the phone began to struggle. The camera app started to freeze, taken photos were never recorded, and the phone took forever to reboot. At times, apps stopped starting up and the phone would hang. Removing the microSD card cured everything, so I decided it was the culprit, and seeked to recover as much as I could from the card.

Copying from the card was fast for a few files, and then would stop and stall for a long time before failing with an I/O error.

It wasn’t just one or two files. A large number of files succumbed, including my TWRP backup of the phone. To copy it off and work out exactly which files were affected would take a long while, and because of card misbehaviour, ddrescue was not really as viable as it could be.

The card had a tendency on hitting some error to hang for a while then completely drop off the bus, requiring a cycle of the card (unplug/replug) to regain access. Worse still, some affected sections appear to be directory entries in the FAT, thus even listing certain folders was not reliable.

As I didn’t want to waste a lot of time, I devised a method to copy as much as possible in as short a time. Using Windows 7, I copied all files to a new folder, but when the card struggled, I pulled the card from the reader, provoking this error …

… while at the same time, plugging the card back in, allowing enough time to recognize the card and then hitting skip to bypass the “damaged” file.

In all, I only lost 9 of about 1000 photos, the backup of the phone, and a few random temporary download files. Nothing too major, although if you’re going to yell at me to “use cloud backup”, I’d have to decline since I really don’t want to tie up my limited upload bandwidth with that nonsense. Sharing my 1Mbit/s with another two family members that do use such systems and their friends is enough …

The Curse

Now came the time to consider returning the card under warranty. It had a “limited lifetime” warranty, and the failure occurred in less than a year.

The HDTune Pro error scan failed after 2356 errors, and it seemed the card had fully given up returning data at a point. The errors were real.

But I could not let a card containing my own personal data out to return, so I wiped the card. Unfortunately, as it turned out, post full formatting, it was again able to store and retrieve data across its entire surface correctly.

The fault had cleared, thus making me ineligible to return the card, probably due to internal reallocation or reprogramming of the faulty flash cells. However, it seems highly likely that the issue will re-manifest itself into the future.

After this experience, I cannot recommend any Sandisk Ultra cards. It seems the whole planar TLC memory thing has gotten out of hand, and that their cards of exceedingly poor endurance. This is the third Ultra card I’ve had fail in 2016, and it’s not because I use them harshly at all. In fact, that card had only been fully cycled in commissioning testing, and then was never filled completely. It was used in a phone as photo storage, and never even received a load of video/audio. The other two cards that had failed started similarly, but ended in complete lack of recognition of the cards (a 32Gb and a 64Gb card).

The Final Nail

Unfortunately, it wouldn’t be the end if there wasn’t a little twist. When putting the card back into the phone, I had it formatted as exFAT as per SDXC standards. I didn’t realize (or remember) that the Xiaomi Redmi Note 2 did not support exFAT and required it formatted FAT32. When the message saying “external SD blank or unsupported filesystem” came up, and an offer to format the card correctly was proposed, I leapt at it without thinking twice.

It seems that an interaction between this command and the custom recovery (TeamWin Recovery Project) meant that instead of formatting the external SD card as it should have, it wiped the internal SD leaving the unit back to factory defaults and me without a backup to restore from thanks to the card failure.

So, four hours of my time was spent flashing the newest weekly ROM (why not?) and reinstalling everything … just to get it back to life … with its swollen battery. I’m flying out in four weeks – I really don’t need this.


It’s a shame but it seems the Sandisk brand no longer represents the quality it once did. But that’s not the only brand I’ve had issues with – Lexar is also part of the group too.

As a result, I can’t really recommend the Sandisk Ultra as a good choice anymore – I now look towards Toshiba and Samsung instead, as none have faultered in my hands yet.

However, it seems quite likely that the whole trend towards cheaper flash memory devices and TLC memory means that reliability is on the down-hill. I’d hate to think what people using them for constant data writes (e.g. data-loggers, dash-cams, surveillance-cams) will see in terms of endurance.

About lui_gough

I'm a bit of a nut for electronics, computing, photography, radio, satellite and other technical hobbies. Click for more about me!
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3 Responses to Failing: Sandisk Ultra microSDXC 128Gb (Class 10, UHS-I, Up to 80MB/s)

  1. Wiping the incorrect storage sounds like a pretty serious design fail. That was painful to read.

  2. Rudgie Mar says:

    How do you do post full formatting?
    My Sandisk Ultra 64GB SDXC is also having the same problem. I wanna use it again

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