tool to completely fill a drive with random data and ensure it can be entirely correctly read back
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Stressdrive is a Mac OS X command-line tool meant to verify correct operation of a drive. It does so by filling a drive up with random data and ensuring all the data can be correctly read back.

It was written to verify correct operation of de-duping SSDs, but it can be used with normal HDDs or any rewritable block storage device.

DANGER: stressdrive will overwrite, without warning, all data on the given drive. Be sure to double-check the drive you're aiming it at (Disk > Select Drive > Info > Disk Identifier).


sudo ./stressdrive /dev/rdisk1

Sample Run

$ sudo ./stressdrive /dev/rdisk9
blockSize: 512
blockCount: 468862128
speedScale: 16x
scaled blockSize: 8192
scaled blockCount: 29303883
writing random data to /dev/rdisk0
writing 100% (block 29303002 of 29303883)
1779f30a231c1d07c578b0e4ee49fde159210d95 <= SHA-1 of written data
verifying written data
reading 100% (block 29302306 of 29303883)
1779f30a231c1d07c578b0e4ee49fde159210d95 <= SHA-1 of read data

That run took about 10 hours on a 240GB SSD.

"How is this better than Disk Utility's 'Zero Out Data'?"

Some SSD's de-duplicate stored blocks. For these "filling" it with zeros if actually just modifying one or two actual mapping blocks over and over again. It's not a real test of the SSD's hardware.

"How is this better than Disk Utility's '7-Pass Erase'?"

Stressdrive only overwrites the drive with data once (so it's 7x faster) and then verifies all the data is correctly read back (which Disk Utility doesn't do at all).

Jens Ayton informs me 7-Pass Erase uses fixed patterns, so de-duping may be an issue there as well.

"Pshaw! I could do this with dd, /dev/random & shasum!"

Indeed you could. I prefer a minimal focused tool whose operation is fixed, its source simple+readable and offers good built-in progress reporting.


Stressdrive should be easily portable to other Unixes if anyone wants to do that and toss me a Pull Request.