An SD card, or Secure Digital card, is a type of removable flash memory card commonly used in digital cameras, mobile phones, camcorders, and other portable devices to store photos, videos, music, and other files. On a Mac computer, SD cards can be inserted into a built-in or external card reader to transfer and access files stored on the card.
Monitoring the health of your SD cards is important to ensure you can reliably store and retrieve data. A failing or damaged SD card can lead to data loss or corruption, making files unreadable. Checking for signs of SD card issues and running diagnostics can help identify problems early before they result in permanent data loss. This guide will cover various methods to test and monitor the health of SD cards on a Mac.
Signs of a Failing SD Card
There are several signs that may indicate your SD card is failing or has become corrupted on your Mac:
Slow transfer speeds – If you notice read/write speeds are much slower than usual when transferring files to/from the SD card, this can be a sign of a problem. Healthy SD cards should have fast data transfer rates. A slow, lagging SD card is often a failing one.
Frequent read/write errors – Error messages when trying to access files on the SD card, trouble copying files to/from the card, or problems opening photos/videos can indicate issues. The SD card may be damaged and struggling to reliably read/write data.
Corrupted files – Videos and photos that won’t open or appear corrupted/damaged are a clear warning. Data corruption happens when the SD card cannot reliably store the files. Back up any retrievable data immediately.
Unmounting issues – An SD card that randomly unmounts itself or fails to mount when inserted into your Mac likely has underlying problems. This tends to happen when the card reader struggles to communicate with a damaged SD card.
Using First Aid to Check SD Card
One way to check the health of your SD card is by using Disk Utility’s First Aid tool. Here’s how to use First Aid to verify and potentially repair issues with your SD card:
1. Open Disk Utility on your Mac. You can find this in the Utilities folder within the Applications folder.
2. In the sidebar of Disk Utility, select the volume that corresponds to your SD card.
3. Click on the “First Aid” button at the top of the Disk Utility window.
4. Click “Run” to begin the First Aid process. This will check the SD card for errors and attempt to repair any issues it finds.
5. Once completed, review the First Aid report. This will let you know if any errors were found and if they were able to be repaired. If the First Aid tool is able to fix errors on your SD card, that’s a good sign it’s still relatively healthy.
6. If First Aid is unable to repair issues with your SD card, that likely indicates there are more serious problems and you may need to re-format or replace the card.
Checking SMART Status
One way to check the health of your SD card on Mac is by using the smartmontools command line utility to view the SMART (Self-Monitoring, Analysis and Reporting Technology) data. This can give you insight into any issues or failures the SD card may be experiencing.
To check the SMART data, first insert your SD card into your Mac’s card reader. Then open the Terminal app and type the following command:
smartctl -a /dev/disk[disk identifier]
Replace [disk identifier] with the actual disk identifier for your SD card, which you can find by running diskutil list in Terminal. This will output the full SMART data report for your card.
Two important SMART attributes to check are the pending sector count and ECC error count. Pending sectors indicate parts of the SD card that are unreliable and pending reallocation. A rising pending sector count is a sign of failure. ECC errors refer to correctable errors that occur when reading data from the NAND flash memory. Higher ECC error counts indicate the card is having trouble accurately reading data from the flash memory and is at greater risk of uncorrectable read errors.[1]
If the SMART data shows high pending sector or ECC error counts, it’s a good indication your SD card is failing and should be replaced.
Using a Benchmark Tool
Benchmark tools like Blackmagic Disk Speed Test provide a way to test the read and write speeds of your SD card.
Comparing the speeds reported by Blackmagic to the expected performance specifications of your SD card can help identify issues. Most SD cards will be rated for a minimum read and write speed. If your card is consistently testing below its rated speeds, that’s a sign it may be failing or degrading.
Slow and inconsistent speeds in a benchmark test often point to problems with the SD card, especially if speeds fluctuate drastically between runs. Healthy cards should deliver consistent performance. So if your card starts off testing fast but then slows down dramatically, that likely indicates it’s time to replace it.
Monitoring Usage in Activity Monitor
The Activity Monitor app built into macOS provides detailed insight into how your Mac’s resources are being used. This includes monitoring the read/write activity on external drives like an SD card.
Frequent spikes in usage shown in the Disk tab of Activity Monitor may indicate potential problems with the SD card. The app allows you to view real-time disk activity as well as historical usage. If the SD card shows abnormally high read/write levels, this could signify it is failing or damaged in some way.
By keeping an eye on the Activity Monitor when accessing files on the SD card, you can check if performance dips or usage spikes occur. If everything appears normal, the issue likely lies with the SD card itself. But if your Mac’s resources are taxed whenever the card is accessed, the problem may be with the card reader instead.
Checking the Card Reader
If your SD card is not being detected, the issue could be with your Mac’s built-in SD card reader. Try using a different external card reader if you have one available to see if the SD card shows up. Persistent issues detecting the SD card across multiple readers likely indicate a faulty card reader.
The SD card readers on Macs can fail over time with regular use. If you’ve ruled out the SD card being the problem, then a faulty SD card reader may need to be repaired or replaced. Check forums and communities to see if other users with your Mac model have reported issues with the SD card reader.
For example, some users have reported SD card readers intermittently working or not being recognized at all, especially after updating to new MacOS versions. Trying SMC and PRAM resets may help, but hardware issues with the reader may require repair or replacement.
If you rely on using an SD card with your Mac, getting an external USB card reader can help provide a reliable workaround if the internal SD card reader develops issues. But if the built-in reader completely stops working, then your Mac may need service to address the SD card reader problem.
Trying a Different SD Card
Sometimes errors reading an SD card can be caused by the card itself becoming corrupted or damaged over time. Trying a known, good SD card with no issues can help rule out a problem with the suspicious card itself. If a working SD card also experiences read errors or is not detected properly in your Mac, the issue is likely with your computer’s SD card reader hardware or drivers, not the card[1].
Test reading and writing files on a different, working SD card that you know is not corrupted or damaged. If the replacement card functions without issues, the original card may need to be reformatted, repaired or replaced. However, if the same problem repeats when using the known good SD card, then your Mac likely has an issue with the SD card reader or drivers that is preventing read/write access. This means the computer may require troubleshooting itself rather than just the SD card[2].
Before replacing an SD card, double check the card reader hardware by trying multiple cards, updating software drivers, using a USB-based reader, or having your computer serviced. An inexpensive SD card is often easier to replace than an entire computer. But if multiple cards fail in your Mac’s built-in reader, then it is certainly an issue with the computer rather than just a problematic card.
[1] https://www.cleverfiles.com/help/sd-card-not-showing-up.html
[2] https://macpaw.com/how-to/sd-card-not-showing-mac
Reformatting the SD Card
Before reformatting your SD card, it’s important to back up any data you want to keep. Copy files from the SD card to your Mac or external storage.1
To reformat your SD card on Mac, use the built-in Disk Utility app:2
- Connect your SD card to your Mac using a card reader or built-in SD card slot.
- Open Disk Utility (located in Applications > Utilities).
- In the sidebar, select your SD card drive, not the volume name below it.
- Click Erase at the top.
- Give your SD card a name.
- Choose a format like APFS or exFAT.
- Click Erase to reformat the drive.
If needed, you can also repartition your SD card to change the allocation of storage. Just click Partition in Disk Utility before erasing.3
Reformatting will erase all data on the card, resolving many performance issues and preparing it for reuse.
When to Replace an SD Card
SD cards have a limited lifespan and will eventually fail with age and heavy usage. As an SD card gets older, data corruption and read/write issues become more likely even if the card is still functioning properly. The typical lifespan of an SD card under normal usage is estimated to be around 10 years or more according to the SD Association FAQ. However, heavy usage in a camera or other device that writes data frequently can shorten this lifespan.
If the steps above to check and repair your SD card health do not resolve performance issues, it may be time to replace the card. An SD card that is repeatedly showing signs of corruption or failing to read/write data likely means it is reaching the end of its usable life. The only way to get a fully functioning SD card again is to purchase a new one. Before replacing the card, make sure to copy any important files or data from the old card if possible. Then, safely format or physically destroy the worn out SD card to erase data before disposing of it.