Comments on: Enabling and Testing SSD TRIM Support Under Linux

By: Zachary Sonicfast

Zachary Sonicfast — Sun, 24 Mar 2013 21:07:00 +0000

Why not just have discard already built into Linux? That way no manual manipulation would be needed.

It would be nice to have a point and click method to run trim (discard) manually without all the typing. Right click on a drive and left click on trim sorta thing.

I have discard put into my fstab but the system seems to be getting really slow on startup.

By: codeboy

codeboy — Tue, 01 Jan 2013 07:03:00 +0000

If it used to have valid testfile data before you deleted it, and after you delete the file it shows either all 00 or all FF then trim is working. The difference is due to different technologies, NOR flash vs NAND flash.

NOR flash must write all data to 00 before it can be erased (to FF)

NAND flash does not need to do this, and can quickly erase to FF.

Finally, both technologies require any block to be in the erased state before it can be rewritten with data.

The drive that shows all 00 is probably using NOR flash and wrote all 00 but did not erase it yet. That might come later, when the controller’s garbage collector erases the blocks.

The drive that shows all FF is probably using NAND flash and quickly erased the block and marked it free to use.

In both cases, it would appear to me that TRIM is working as intended.

For some flash technologies, an empty cell is a 0 bit. For other flash technologies, and empty cell is a 1 bit. Thus an empty flash block would be filled with 1′s and would show up as FF after trim.

By: Rob Williams

Rob Williams — Thu, 27 Dec 2012 22:36:00 +0000

Those should be 0s, so no, I don’t think so. The fact that the characters are all the same leads me to believe it’s just bunk data (as if the drive was purposely filled).

You may wish to look at the fstrim tool instead:

http://manpages.ubuntu.com/manpages/oneiric/en/man8/fstrim.8.html

I’ve heard that it’s recommended over the “discard” option mentioned in this article, but I haven’t had a chance to give it a good test. The idea would be to set up a scrip that would run once per day to clean all deleted blocks.

By: Tiago Ventura Mendes

Tiago Ventura Mendes — Thu, 27 Dec 2012 22:34:00 +0000

Good evening.

I got “f” instead of “0″

IS it enabled?

Thank you.

By: Tiago Ventura Mendes

Tiago Ventura Mendes — Thu, 27 Dec 2012 22:31:00 +0000

Good evening.

I got this instead:

reading sector 119807832: succeeded

ffff ffff ffff ffff ffff ffff ffff ffff

IS it enabled?

Thank you.

By: Julio Bêtta

Julio Bêtta — Tue, 20 Nov 2012 21:46:00 +0000

thanks!!!

By: matuog

matuog — Tue, 13 Nov 2012 00:32:00 +0000

a very nice article! thank you!

By: Rob Williams

Rob Williams — Mon, 12 Nov 2012 18:58:00 +0000

I’m glad the article proved useful!

By: fsk141

fsk141 — Mon, 12 Nov 2012 18:30:00 +0000

Thanks for this, been planning on setting up trim support with JFS on the new 3.7 kernel. Now I’ll know how to easily test that it’s working.

Appreciate it!