Yes but I believe the OP's concern is the write cycles for an SSD which zeroing out the data would consume a significant number of. Honestly this is an issue I have not yet had to encounter so I am curious to know what the best answer is.
Exactly! SSDs haven't been around long enough; every article I read about long-term stability ends up being conjecture. Can't find a concrete "This is the proper way SSDs should be handled and reformatted" guide anywhere at the moment.
Okay... here's the deal. SSDs use NAND chips to store data, and those chips have individual cells on them that will begin to degrade after a given number of write cycles. Some of the newer SSDs use a type of NAND called TLC NAND, and it can handle ~1,000 life cycles. Give
this article a read.
So let's say you have a TLC NAND SSD. If you look in the article you will see a chart that shows it would begin to degrade in 11.7 years IF you wrote 10GB to the drive EVERY SINGLE DAY, which for most of us is not going to happen.
So back to your question. When you do a secure erase with a one pass of zeros, you have just "used up" one of the 1,000 write cycles of every NAND cell on the drive. As a practical matter (doing the math off 11.7 years) this means the SSD will begin to degrade in 4,265 days instead of 4,270 days.
Remember, this is with the TLC NAND at 1,000 life cycles. MLC NAND has 3,000 life cycles, making this even less an issue.
Short version. I would not run secure erase every week, but it will not matter much if you do it occasionally.
IMO everybody is a little too concerned about this issue with SSDs.
Back to your first post though. If you are not concerned about data recovery, there is no reason for you to secure erase. Just format the drive normally to Mac OS Extended and use it.
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From posts by those more experienced with SSDs here, I have concluded that SSDs slow down as all the cells are written-to (programmed), whether by data, all '1', or all '0', and they must be "reset" to a non-programmed state to regain their speed. This is normally done with the controller "garbage collection" and/or by the OS with "trim". Otherwise, when data is written to a programmed location, that block must first be reset, then written, causing the slower performance. Thus, performing a "secure erase" whereby all ''0' data is written to the entire array without allowing idle time for the cleanup, is actually the worst thing that can be done to a SSD.
I have seen no "quick initialize" methods in OS X to reset a SSD back to its virgin out-of-box state. However, I have seen discussions on how that can be done if you can put the SSD in a Linux or Windows environment and run base-level commands.
I would like to see a method for doing this SSD reset within OS X if anyone knows how.
You are correct that a Disk Util secure erase with zeroes, would put the drive in a state where write speed is slowed due to the state of the cells, but if left to idle for a time after that the built in garbage collection of the drive will restore this to like new performance. If you look at some of the Anandtech SSD reviews they have a great chart in the TRIM performance section that shows drive speed recovery both with and without TRIM. They all recovery either way, although they recover faster with TRIM.
Another way to instantly restore like new performance in OS X is to install the TRIM hack then boot to single user mode and enter the command "fsck -fy". This will TRIM all unused blocks on the drive.
