Erasing everything on Cisco IOS flash storage

Files on the flash: storage before erasing:

3560sw-1#dir flash: Directory of flash:/

2  -rwx         736   Mar 1 1993 00:10:59 +00:00  vlan.dat
3  drwx         512   Mar 1 1993 00:13:49 +00:00  c3560-ipservicesk9-mz.122-58.SE1
5  -rwx         850   Mar 1 1993 00:07:11 +00:00  config.text
6  -rwx           5   Mar 1 1993 00:07:11 +00:00  private-config.text
7  -rwx        2072   Mar 1 1993 00:07:11 +00:00  multiple-fs

27998208 bytes total (9958400 bytes free)

Erasing flash:

3560sw-1#erase flash:
Erasing the flash filesystem will remove all files! Continue? [confirm]
mifs[4]: 0 files, 1 directories
mifs[4]: Total bytes     : 27998208
mifs[4]: Bytes used      : 1024
mifs[4]: Bytes available : 27997184
mifs[4]: mifs fsck took 0 seconds.

Erase of flash: complete

flash: is empty:

3560sw-1#dir flash:
Directory of flash:/

No files in directory

27998208 bytes total (27997184 bytes free)