Re: SSD Analyzer Tool

While I like the math, I'm not sure it's entirely that straightforward. First, you're assuming that the first failure occurs after 3000 writes. I'm really not sure that's the case or if rather that's more of a MTBF sort of number. But leaving that, I don't know that simply multiple the GB by 3000 is going to work. I believe you can only use the unused part of the disk to rotate your writes. Thought exercise: if the disk were 80% full and if those files stayed relatively static, you'd reduce your write pool accordingly. So now you've dropped your space by a factor of five. Further, I think you have to deal with fragmentation; either you have to keep a big index of free space, or you have to effectively have a hard sector size with all that entails.

Personally, I'd be a little leery of dumping all my data to SSD just yet. I'd probably want the dust to settle just a little bit. We've gone through this before (does anyone remember "bubble memory")?

Joe

Take a 177GB drive and assume cells can start failing after 3000 writes,
there's no slack space/overcapacity, but the drive has a good wear leveling
algorithm. That would suggest you can write 531,000GB before the first
cells start to fail. If you figure a 5 year duty cycle for the drive you
can write 290GB per day.

Now, extend that by adding in for the slack space. Most SSDs have 7-11%
extra capacity but of course it can be higher. Keeping with the worst-case
picture, 7% bumps the daily writes up to 311GB, which works out to about
13GB/hour or 216MB/minute for every minute, 24 hours per day, for 5 years.

If the IBM drives use SandForce controllers, extend that even more as the
SF controllers do both compression& data deduplication.

If IBM speced cells that are good for 10K writes v. the 3K minimum, then
the writes-before-a-cell-wears-out more than triples.