SSD Write Endurance 25nm Vs 34nm

[johnw]

Nothing too monumental, but on my setup (2R0 Vertex 2 50GB with FW1.10, 32KB stripe), Anvil's "67% Compression with No Dedup" setting has a write amplification of ~1.185x.

Interesting. Sandforce could not compress it at all. Makes me wonder about what Anand's SSDs had written to them with his repeated claim of 0.6 WA.

[Vapor]

So that is a total of A = 271.9788 GB written by Anvil's app in four trials, in which (I think you mean) the SMART attribute increased by 256.

271.9788 / 256 = 1.0624172

(1024/1000)^1 = 1.024000
(1024/1000)^2 = 1.048576
(1024/1000)^3 = 1.073742
(1024/1000)^4 = 1.099512

So the units of the SMART attribute are hard to explain. They are closest to GiB, but still about 1% off from GiB.

I guess there is a bug in either the Sandforce firmware or Anvil's app.

Yeah, A = 272GB or 253.3GiB for an increase of 256 in the SMART attribute. Each 64 increase was very consistently 63.2-63.4GiB too. Until more data says otherwise, I'm going to take SMART attribute readings for SF-1200 to equal GiB.

Just ran 135.95GiB of writes to my X25-M 80GB G1 and it showed up as 136.72GB in SMART (and damn my G1 is slow and stuttery with this...35MB/s and a stall once every 5-10 seconds). It would be good if someone could double-check this with more writes--my G1 just doesn't want to take part in the party.

Started it back up on my Vertex 2s with Task Manager running, will let it run for awhile and see what differences there are, if any.

[Vapor]

Started it back up on my Vertex 2s with Task Manager running, will let it run for awhile and see what differences there are, if any.

354.69GiB written and reported by Anvil app vs. 354.6975GiB reported by Task Manager. Looks like any discrepancy is at the disk level or not there at all and just showing up due to the way I was measuring.

Going forward, it looks like A) it's totally fine to use Anvil's reported writes and B) SMART values are most likely in GiB.

[johnw]

Going forward, it looks like A) it's totally fine to use Anvil's reported writes and B) SMART values are most likely in GiB.

I agree with A. But not B. From your data, it seems like the Sandforce SMART attribute has a bug. The attribute reports 256 of SOMETHING when Anvil's app reports 253.3GiB = 271.9788GB. The SMART attribute may be INTENDING to be in GiB, but what it is actually reporting is a unit that is about 98.9% of a GiB (about 1,062,000,000 Bytes). As you said, it is consistent -- consistently short of a GiB, meaning the firmware is recording 1% more writes than actually occurred if it is intending to be GiB. Alternatively, for all we know, it could be INTENDING to be in GB, but somehow it is missing some writes -- about 6%.