Sandforce Life Time Throttling

[Ao1]

^ SMART attribute 177 increased yesterday to 14 giving a more respectable WA figure, but I’m still not 100% convinced that it is recording P/E cycles. Samsung support stated: “The raw value on this attribute is how many times it can prolong the life of a specific block” , which might explain why it could appear erratic.
It might refer to something like a write combining event that was able to prevented a block erase. I’ll continue to monitor until it gets to 15 to see how things progress, but somehow I don't think SMART attribute 177 is quite figured out just yet.

[Ao1]

Back to the 520.

This is a quick rundown to hone onto block sizes and QD’s that result in either good or bad WA. The results are a bit rough and ready due to the small amount of writes for each category and the limitation of 1GiB increments for NAND writes, so results could vary, especially for the small blocks at QD1.
A pattern does seem to immerge though

• 0 fill appears equally good regardless of block size or QD, except 1K
• Incompressible is actually quite impressive, except 1K

So it seems that random writes of 4K or less, regardless of compressibility, have (to a varying degree) a disproportionate impact on WA, which would explain why WA was coming out so high when just monitoring typical OS and app workloads.

[canthearu]

Awesome work Ao1, wish I had the option to thank as well.

I definitely agree, from my own observations over the last week, that very light OS activity can produce bad WA on the sandforce drives. I did get my drives down to 1 or 2 gig per day NAND writes a day though. (24/7, just sitting doing not much)

I don't really think it is a problem though, the usage is so light that it would take decades to wear the drive out. The controller would have panicked for some reason or another long before that