Is Trim automatic in Linux with an SSD?

[Fox]

Here's a technical question. I recently installed an OCZ SSD in my netbook, which I use to run Ubuntu Netbook Remix(UNR) 9.10. The most recent version of the firmware, which was installed on my SSD, provides Trim support. So does the Linux kernel in UNR 9.10. My question is whether the SSD will automatically "clean" itself of erased blocks under my system, or whether I need to periodically run a program to clean these out?
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Mini 1: 2.3 ghz Core i5; 8 gb RAM, Corsair 240gb SSD, 500 gb Seagate XT
Mini 2: 2.26 ghz Core 2 duo, 8 gb RAM, 500 gb Seagate
Also a Cube, 13" MacBook Air, 20" 2.66 ghz iMac & 11.6" Acer 1810TZ running Ubuntu, Mint & openSuse

[Chris..S]

I've kind of half been following this, but I'm no expert. Its my understanding that TRIM support is in the kernel ( since 2.6.28 ) but that the only file system which supports it is ext4.

TRIM requires FS support. Its the FS that deletes files and frees blocks, so only it can tell the drive that blocks are "free" and allow TRIM to work its magic.

I think 9.10 uses ext4 as the default FS for fresh installs. I.e. it won't change the FS on upgrading. So if you did a fresh install of 9.10, you should have ext4 and ability to take advantage of TRIM. I don't know how you take advantage of TRIM. This thread may help.

[Fox]

Thanks, Chris..S. I posted a similar query on an OCZ forum. I now know that TRIM is not automatic, and won't be in Ubuntu until version 10.10. I am using ext4 partitions, and there is a program I can run periodically on Linux to invoke TRIM.
_________________
Mini 1: 2.3 ghz Core i5; 8 gb RAM, Corsair 240gb SSD, 500 gb Seagate XT
Mini 2: 2.26 ghz Core 2 duo, 8 gb RAM, 500 gb Seagate
Also a Cube, 13" MacBook Air, 20" 2.66 ghz iMac & 11.6" Acer 1810TZ running Ubuntu, Mint & openSuse