Advanced Format Drives

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What is it?

Advanced Format or 4K Hard Drives use a different internal organizational scheme to pack more data into the same physical space (the technical way of putting it is they have increased areal density). In 2009, this didn't exist. In 2011, this will be the new standard. Therefore, 2010 is the awkward transitioning period.

As of January 2011, newer versions of unRAID now support Advanced Format drives natively. See below.

unRAID 4.6.1/5.0-beta3 or newer

Newer versions of unRAID are fully compatible with Advanced Format drives, see here for more information.

unRAID 4.6/5.0-beta2 or older

You have to take action on certain consumer drives on the market today in order to make them compatible with these older versions of unRAID. Certain drives may even be completely incompatible. As of January 2011, here's a list of the affected drives and appropriate action:

Manufacturer Series Action
Western Digital (WD) WDEARS Install a 2.54MM type jumper on pins 7 & 8 before installing the drive into an unRAID server
Samsung HD204UI Do not use! Samsung F4 drives are incompatible with unRAID, see here for details

What does the jumper actually do?

It puts the drive into compatibility mode. This will improve performance in unRAID since the partition starting on sector 63 is then fooled into using a sector (64) aligned on the 4k boundaries.


Installing a jumper on a drive that already contains data will likely result in data loss.

What if I already have an Advanced Format drive in my array that isn't in compatibility mode (i.e. no jumper)?

The best case scenario is that you are suffering a 20-30% performance penalty. The worst case scenario is that your server may be even slower than that. If you simply add a jumper and do nothing else, all the data on the disk will be offset from what is expected, and the OS will consider it hopelessly corrupted.

What should I do if I already have an Advanced Format drive in my array that isn't in compatibility mode (i.e. no jumper)?

Below is a simple procedure to rectify this situation. If you are extra paranoid about data loss and if you have the space to spare, it is recommended that you back up all data on the Advanced Format drive before performing this procedure.


PERFORM THE FOLLOWING STEPS ON ONLY ONE DRIVE AT A TIME, OTHERWISE YOU WILL LIKELY LOSE DATA. Also, this procedure will put your unRAID server in a state without parity protection for the amount of time it takes for a Data-Rebuild to complete.

  1. Run a parity check. If there are errors, do NOT proceed, seek help in the forums.
  2. Stop the array, power down the unRAID server.
  3. Put the Advanced Format drive into compatibility mode (take the action specified on the chart above). This may involve physically removing the drive from the server, or it may not, depending on your configuration.
  4. Power up the unRAID server.
  5. Go to the 'Devices' page and unassign the Advanced Format drive. Then go back to the 'Main' page and Start the array. The missing disk will be running in emulated mode, and your array will not have parity protection at this point.
  6. Stop the array, go back to the 'Devices' page, and assign the Advanced Format drive to the missing disk slot.
  7. Go back to the 'Main' page and Start the array. A Data-Rebuild should begin. Let it finish (this will take a long time).
  8. Once the Data-Rebuild is complete, run another parity check. After the parity check completes with no errors, then your parity protection is restored. If the parity check returns errors, seek help in the forums.

Rinse and repeat the above procedure for all Advanced Format drives not running in compatibility mode. DO NOT PUT THIS OFF, since the longer you wait, the more likely you are to run into trouble.

Should I install the jumper before or after preclearing the drive?

Before. There is danger involved in installing the jumper after:


If you put the jumper into place after the pre-clear script has been run or it is added to unRAID directly the disk will substitute sector 1 when accessing sector 0, 2 when accessing 1 ... 64 when accessing 63, 65 when accessing 64, etc. This will improve performance since the partition starting on sector 63 is then fooled into using a sector (64) aligned on the 4k boundaries.

The "partition table" that holds the original partition table, master boot record and pre-clear signature looked for by unRAID will not be visible. They were in sector 0. (no longer visible with the jumper in place) The "cleared" sector 1 (now presented as 0) will be completely blank... as you cleared it to be all zeros.

The disk will still work perfectly in unRAID, but unRAID will perform a clearing and partitioning of the disk on its own. It will do this if you have already assigned a parity disk to your server because it will not detect a pre-clear signature.

In simple terms apply the jumper BEFORE adding the disk to unRAID. Applying the jumper to a HDD already in unRAID will likely result in data loss.

What's the backstory? Why is this happening? Why can't we just leave well enough alone?

To quote Seagate directly: "International Disk Drive Materials and Equipment Association (IDEMA) have agreed that beginning January 1, 2011 all new product releases with SATA interfaces will support Advanced Formatted media."

Many disk drive interface technologies already allow for increased sector sizes. However, the 512-byte sector has been the standard for over 30 years. As a result, many points in a computer system (systems like personal computers, servers, DVRs, PSPs, and cell phones) have become inflexible and only work using 512-byte sectors.

To maintain compatibility with these devices, Advanced Format media emulates a 512-byte device by maintaining a 512-byte sector at the drive interface. The larger sector bring efficiency advantages because as the total size of drives increase, less sectors have to be used, and less ECC data overall has to be written, physical saving space. The downside is that there are issues of compatibility with older operating systems, however the drives will contain a "512B emulation mode" (at a small performance loss [1]) for the foreseeable future.

The Advanced Format technology paves the way for the drive industry to continue to increase areal density and develop higher capacity drives. Advanced Format technology improves burst error correction by 50% through the use of larger ECC (error correction code) code word.

Will unRAID support Advanced Format drives in the future?

The future is now! See the unRAID 4.6.1/5.0-beta3 or newer section above.