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I'm investigating the use of SSDs for a program that does some very sustained sequential reads. I have seen "TRIM" in capitals in various online references and explanations, but no reference to what the acronym stands for. Wikipedia refers to it in full caps. Looking into some linked reference documents, there is reference to a 'Trim' command.

Is TRIM simply a word? (Computerese strikes again!)

If it isn't an acronym, what is being trimmed?

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2 Answers 2

Not programming related but http://en.wikipedia.org/wiki/TRIM holds your answer.

Btw, I got there by googling TRIM SSD.

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+1 for mentioning how you found the answer. –  BillP3rd Sep 6 '10 at 1:01

No it is called TRIM because something is being trimmed.

Trim is for example a common name of a function in programming languages to delete leading and trailing whitespace from a string which is in a way what TRIM does on SSDs.

I would assume it is written uppercase because TRIM is an ATA-command and they are all written uppercase in the official documents.

And whats being trimmed?

Basically the operating system tells the drive which sectors are no longer in use. Usually when using an HDD this is not necessary because an HDD can just write over existing data. An SSD has to erase a block before it is able to write to it and that operation takes a lot of time. So if the OS can't tell the SSD what sectors are free this erase-operation can only be done at the time you want to save something which leads to very slow write speeds once the SSD has been used a lot.

If the SSD knows about sectors that became free it can erase the blocks in the background and has erased blocks handy as soon you want to save something.

So in a way the space used on an SSD is being trimmed.

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