Difference between revisions of "Solid State Drives/Memory cell clearing"

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== Step 0 ==
 
== Step 0 ==
{{warning| Completijg the following guide WILL destroy ALL data on the SSD!  Make sure that all data of value is backuped before continjuing!}}
 
 
 
Optionally write zeros to every block on the SSD using either dd or dcfldd:
 
Optionally write zeros to every block on the SSD using either dd or dcfldd:
 
   dcfldd if=/dev/zero of=/dev/sdX bs=4k
 
   dcfldd if=/dev/zero of=/dev/sdX bs=4k
  
{{warning|Triple check that the correct drive designation is used in the dcfldd step as there is no turning back once the ENTER key has been pressed!  YOu have been warning.}}
+
{{warning|Triple check that the correct drive designation is used in the dcfldd step as there is no turning back once the ENTER key has been pressed!  You have been warned.}}
  
 
== Step 1 - Make sure the drive security is not frozen ==
 
== Step 1 - Make sure the drive security is not frozen ==

Revision as of 19:01, 19 May 2012

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Introduction

On occasion, users may wish to completely reset an SSD's cells to the same virgin state they were manufactured, thus restoring it to its factory default write performance. Write performance is known to degrade over time even on SSDs with native TRIM support. TRIM only safeguards against file deletes, not replacements such as an incremental save.

Warning: Back up ALL data of importance prior to continuing! Using this procedure will destroy ALL data on the SSD and render it unrecoverable by even data recovery services! Users will have to repartition the device and restore the data after completing this procedure!

Quick N' Dirty

Warning: It is recommended that you read the rest of the article BEFORE you try this!
dcfldd if=/dev/zero of=/dev/sdX bs=4k
hdparm --user-master u --security-set-pass Eins /dev/sdX
hdparm --user-master u --security-erase Eins /dev/sdX

Step 0

Optionally write zeros to every block on the SSD using either dd or dcfldd:

 dcfldd if=/dev/zero of=/dev/sdX bs=4k
Warning: Triple check that the correct drive designation is used in the dcfldd step as there is no turning back once the ENTER key has been pressed! You have been warned.

Step 1 - Make sure the drive security is not frozen

Issue the following command:

# hdparm -I /dev/sdX

If the command output shows "frozen" one cannot continue to the next step. Most BIOSes block (do no allow) the ATA Secure Erase command by issuing a "SECURITY FREEZE" command to "freeze" the drive before booting an operating system.

A possible solution for SATA drives is hot-(re)plug the data cable (which might crash the kernel). If hot-(re)pluging the SATA data cable crashes the kernel try letting the operating system fully boot up, then quickly hot-(re)plug both the SATA power and data cables.

  • It has been reported that hooking up the drive to an eSATA SIIG ExpressCard/54 with an eSATA enclosure will leave the drive security state to "not frozen."
  • Placing the target system into "sleep" (Clevo M865TU notebook, Fujitsu T2010 notebook, Dell XPS M1330) and waking it up again has been reported to work as well; this may reset drives to "not frozen". In case you are booting from USB, you need a distribution, that runs entirely in RAM, like [1], see the grml2ram option. Run echo -n mem > /sys/power/state to set the computer to sleep.
  • Hooking up the drive to a USB 2/3 port does NOT work, as you need to issue IDE commands which is only possible via IDE/SATA connection.
  • Make sure drive security is disabled in BIOS, so no password is set.
Security: 
        Master password revision code = 65534
                supported
        not     enabled
        not     locked
        not     frozen
        not     expired: security count
                supported: enhanced erase
        2min for SECURITY ERASE UNIT. 2min for ENHANCED SECURITY ERASE UNIT.

Step 2 - Enable security by setting a user password

Note: When the user password is set the drive will be locked after next power cycle denying normal access until unlocked with the correct password).

Any password will do, as this should only be temporary. After the secure erase the password will be set back to NULL. In this example, the password is "Eins" as shown:

# hdparm --user-master u --security-set-pass Eins /dev/sdX
security_password="Eins"
/dev/sdX:
Issuing SECURITY_SET_PASS command, password="Eins", user=user, mode=high

As a sanity check, issue the following command

# hdparm -I /dev/sdX

The command output should display "enabled":

 Security: 
        Master password revision code = 65534
                supported
                enabled
        not     locked
        not     frozen
        not     expired: security count
                supported: enhanced erase
        Security level high
        2min for SECURITY ERASE UNIT. 2min for ENHANCED SECURITY ERASE UNIT.

Step 3 - Issue the ATA Secure Erase command

# time hdparm --user-master u --security-erase Eins /dev/sdX

Wait until the command completes. This example output shows it took about 40 seconds for an Intel X25-M 80GB SSD, for a 1TB hard disk it might take 3 hours or more!

security_password="Eins"
/dev/sdX:
Issuing SECURITY_ERASE command, password="Eins", user=user
0.000u 0.000s 0:39.71 0.0%      0+0k 0+0io 0pf+0w

The drive is now erased. After a successful erasure the drive security should automatically be set to disabled (thus no longer requiring a password for access). Verify this by running the following command:

# hdparm -I /dev/sdX

The command output should display "not enabled":

 Security: 
        Master password revision code = 65534
                supported
        not     enabled
        not     locked
        not     frozen
        not     expired: security count
                supported: enhanced erase
        2min for SECURITY ERASE UNIT. 2min for ENHANCED SECURITY ERASE UNIT.

Post Process Observation

Note: Once switching from an MBR to GPT partition scheme, this is a non-issue.

I experienced a "glitch" with my Intel X25-M (G2) after doing this procedure. I do not know if it's fdisk's fault or the procedure's fault.

For some reason, after creating two partitions (1st = 68 G and 2nd = rest of drive), the 32 H and 32 S settings weren't retained. Creating just one partition, writing changes, and exiting gave a result consistent with the -H 32 -S 32 settings when checking via the "fdisk -l" command. However, after adding the 2nd partition, writing and running the same "fdisk -l" command, new values for the geometry were shown - they switched to 255/63! The solution was to start fdisk with the 32/32 parameters and write down the number of cylinders, then use cfdisk to do my partitioning.

Example:

# fdisk -H 32 -S 32 /dev/sdb

Command (m for help): p

Disk /dev/sdb: 80.0 GB, 80026361856 bytes
32 heads, 32 sectors/track, 152638 cylinders, total 156301488 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Device Boot      Start         End      Blocks   Id  System
/dev/sdb1              32   132812799    66406384   83  Linux
/dev/sdb2       132812800   156301311    11744256   83  Linux

Here the correct number of cylinders is 152638. I now went into cfdisk and invoked the "geometry" option via: Template:Keypress. I then manually defined the number of heads to 32, sectors per track to 32, and cylinders to 152638. Now I setup my partitions:

                                     cfdisk (util-linux-ng 2.18)

                                          Disk Drive: /dev/sdb
                                    Size: 80026361856 bytes, 80.0 GB
                          Heads: 32   Sectors per Track: 32   Cylinders: 152638

     Name            Flags         Part Type     FS Type               [Label]             Size (MB)
 -------------------------------------------------------------------------------------------------------
     sdb1                           Primary      ext4                                       68000.16     
     sdb2                           Primary      ext4                                       12026.12

Now querying the device via fdisk gave the consistent values.

# fdisk -l /dev/sdb
Disk /dev/sdb: 80.0 GB, 80026361856 bytes
32 heads, 32 sectors/track, 152638 cylinders, total 156301488 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
  Device Boot      Start         End      Blocks   Id  System
/dev/sdb1              32   132812799    66406384   83  Linux
/dev/sdb2       132812800   156301311    11744256   83  Linux