SSD Freeze Mac Pros? 2009 3.33 Nehalem

Question

Are there any know problems using SSDs with this version of Mac Pros? I am using 2 Crucial (256GB M225 SSD Part #:CT256M225), 1 drive for OSX and 1 drive for Win7. The machine consisently locks up using Time Machine in the middle of backups and consistently slow when doing disk writes. I have the latest firmware installed on both drives. The Win7 drive seems to work much faster and I have even swapped drives to make sure that it wasn't drive specific. Any help would be greatly appreciated.

Answer 1

When you erase files on any drive, only the directory entry is cleared. The actual data blocks are unchanged. With a Hard Drive, this is generally not a problem, because the minimum that can be written is one sector/block, historically 512 Bytes. To modify a block, you re-write the entire block.
With a Solid State Drive, that uncleared old data presents an impediment to fast operation, because the smallest block the drive can write is quite large (4K or larger), and you must literally perform an agonizingly slow read-modify-write cycle to change it. If the rest of the block were cleared, the write could be done with a fast destructive write, and would go much faster.
So one way to improve the performance of these drives is to clear out all the old data from time-to-time, and zero out any unused blocks. I use a third-party utility to de-fragment (which by itself does NOTHING for SSD performance) followed by "erase free space with Zeroes". This increase the likelihood that the next bunch of data written can be placed in a large empty disk block without the need for slow read-modify-write cycles.
Remember that if you run Disk Tests to check the performance before and after, you have left all sorts of deleted files all over your drive. These should be removed before proceeding to production work.