E2fsprogs/badblocks

badblocks is a small program for stress testing block devices. Similar to memtest86+, badblocks reads and writes small patterns of bytes to block devices.

Emerge
badblocks comes as part of the package and should be available as part of the default system profile.

Test a drive
To test a drive with visual progress use the  and   options followed by the path to the block device.

Replace  in the command above with the block device that is to be tested. badblocks should run through a series of four tests and return output similar to the following: