Unable to format SD card

disk-utilitysd card

I was using my SD card on my phone. One fine day it showed a message that it was corrupted. I put the card in an adapter and plugged it into my iMac.

I was able to read and copied all I need. I decided to format it anyway and used disk utility to do so.

It said that it had finished erasing, but all the files were still on it.

I tried deleting each folder. But when I ejected and put it back in, the files are still there. I can't format it via my phone either and I am too scared to use the terminal for erasing. Can anyone help me?

Best Answer

It's dead.
Smash it to prevent your data being stolen & throw it away.

If a write error occurs, the firmware controller will switch over to read-only mode to prevent further data loss. This is to all intents & purposes, irreversible.

Related Solutions

Restoring an SD card using a multi-partitioned DMG

Use the dd command-line tool.

Mount the SD
Use "Disk Utility": Select the top level of the SD card and "Get Info". Note the "Disk Identifier" (example disk13)
Unmount all of the volume on the SD, if they are mounted, but do NOT removed the SD card. This is important because the dd will fail if it detects any mounted volumes.

In the Terminal:

If you are not in an Admin account, use "su (admin account name)" to gain admin authority
sudo dd if=/path/to/DMG/file of=/dev/(disk identifier from above) bs=16k

Then wait a long time for the operation to complete. In a 4 GB copy I performed recently to a CF card, it took 21 minutes to finish.

You will eventually get 3 lines stating records in & out and bytes copied. Example:

243528+1 records in
243528+1 records out
3989970432 bytes transferred in 1278.252950 secs (3121425 bytes/sec)

In my case I have been copying .img files to CF cards, hopefully it works just as well for DMG's

MacBook – Crazy Memory usage on Transcend 128GB JetDrive 130 Expansion Card for MBA

As mentioned in my original question, the SD Association (of which Transcend are a member) cite performance impacts as a reason against using standard drive formatters.

However, they have a formatter available for download at https://www.sdcard.org/downloads/formatter_4. On Mavericks, I reformatted my drive using this utility and recopied my files.

The results were as follows:

A single file 14.57GB took 4 minutes to copy. This is the exactly as advertised 60MB/s write speed.
80k files (16GB), however took 92 minutes to copy. which reflects about 5MB/s

In both cases, however, the info window was as expected showing a reasonable amount of memory usage and memory remaining. So, this solved my original problem.

As a comparison, I decided to reformat as a Journaled and found the following:

14.57GB file took 10 minutes to copy, which is only about 50% of the advertised max speed.
80k files (16GB) more importantly took only 10.5 minutes.

For me, sticking with a Journaled format is a no brainer, particularly if writing lots of small files, which I will be. It also may allow me include this on a Fusion drive, although I haven't investigated this yet.

TL;DR - It is probably best to reformat to a Journaled partition as it provides a more consistent write speed of about 30MB/s, no matter the file sizes. ExFAT ranged between 5 to 60 MB/s speeds, depending on the number of files being written (lower number is faster).

UPDATE: Transcend replied to recommended a replacement.

Best Answer

Related Solutions

Restoring an SD card using a multi-partitioned DMG

MacBook – Crazy Memory usage on Transcend 128GB JetDrive 130 Expansion Card for MBA

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