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Just bought a used beast of a desktop pc. The system drive is setup as a Raid 0 SSD (Intel 510 SSD Drives) with 128 each. I will probably not have to many programs beyond office and maybe Adobe CS if I spring for it, I will be keeping big data on a regular hdd.

My question is about setting up TrueCrypt with my configuration. I have not previously done full disk encryption, but I feel that its probably a good idea. I have done some speed tests using file containers on the hdd and the sdd with truecrypt. While there is a huge hit with the SSDs and Truecrypt, it still outperforms the hdd on its own by a good margin, so I think i will be okay for my needs with truecrypt.

I have seen in a few places that they recommend partitioning the drive and leavign some of the SSD not inside truecrypt, does this really make a difference? If so, how much should I leave? Will there be any issue in the Raid0 configuration?

I am not really concerned about all the wear leveling issue, rather loose data and be secure, but since I don't need all that space neccesarily, I would like to optimize my setup for security and speed.

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1 Answer 1

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Short answer: Yes, leaving some unpartitional space can speed up a SSD.

Long answer: Writing data to a SSD usually involves these actions:

  1. Read a large block (on SSD sized blocks, e.g. 64KB)
  2. Change part of the read data (e.g. change 4K data which you just tried to write to SSD)
  3. Find an empty SSD block and write the data.
  4. Update internal pointers so all data of the old block now is found on the new block.

If the SSD has free space then this all goes quite fast.

However if it has no free blocks then this becomes:

  1. Read a large block (on SSD sized blocks, e.g. 64KB)
  2. Change part of that block (e.g. change 4K data)
  3. Find an empty SSD block. Notice there is none.
  4. ERASE a block (this takes a relative long time)
  5. Write to the freshly erased block.
  6. Update administration

If you delete a file and TRIM is enabled that smart things can happen. The drive can know that a block is completely unused and while the drive is idle is can preemptively erase these blocks. Or it could consolidate a few mostly empty blocks in a single block and preemptively erase these dozen blocks. This is a good thing.

But to do all kinds of these things the controller on the SSD needs to know which blocks are in use, and which it can work with. Unless you have TRIM it does not know which part of a filesystem is used. It does not that blocks of unpartitioned space are not used. So if you leave a bit of unpartitioned space if has more blocks to work with. Which is a good thing if you expect to do a lot of fast writing.

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If its using the unencrypted blocks, does that pose any security risk from data being written outside of the encrypted parts? Or is it moving the encrypted parts around in the free space? –  Eric G Jun 2 '12 at 22:36
    
The exact details are up to the firmware, and this is often the 'secret sauce' which differs on SSD from another SSD. Which means we usually do not know. However I see no reason for the firmware to turn off HW encryption on part of the SSD. Checking for that probably adds overhead. Disclaimer: Yes, that is an assumption/guess. –  Hennes Aug 23 '12 at 11:16
    
Removed message. –  Eric G Aug 23 '12 at 13:22
    
My fault for coming back to a question and not properly re-reading the OP. --- The SSD might use internal encryption. You will never notice this unless you set a password/key. This is what I erroneously thought off when I read your question. --- As for TrueCrypt: The host (and thus TrueCrypt ) is not aware of what the SSD is doing with remapping. That part is completely transparent. When it moves some data around the new 'empty' space will stay until erase. Unaltered, and still encrypted by whatever encoding TrueCrypt used. Is that what you wanted to ask? –  Hennes Aug 23 '12 at 13:40
    
I believe so. My assumption then the logical parition is respected physically as well - it will not temporarily write some place which isn't under the truecrypt encryption. –  Eric G Aug 24 '12 at 3:38

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