On Tue, Nov 30, 2010 at 05:42:51PM +0000, Kevin Chadwick wrote: > On Tue, 30 Nov 2010 16:44:51 +0100 > Jan Stary <h...@stare.cz> wrote: > > > On Nov 30 12:32:16, Kevin Chadwick wrote: > > > On Mon, 29 Nov 2010 21:17:17 -0500 > > > Brad Tilley <b...@16systems.com> wrote: > > > > > > > Do they really fail that often? > > > > > > My current understanding is that a mostly empty SSDS electronics will > > > fail before it forgets what it's written but a mostly full and busy SSD > > > may start forgeting fairly soon, unless it shuffles data which would > > > slow it down considerably. > > > > My current understanding is that you treat a SSD as any other disk and > > never even notice that your wd0/sd0 is not a piece of metal rotating > > at 7200RPM, unless you read/write huge amounts of data, which you don't. > > > > Let's not get into that again. > > > > I almost completely agree, but also disagree and yes I'd say it's not > worth getting into again. I would have to check the latest developments > as I can imagine an algorithm which solved the problem during idle > periods or didn't use it's full capacity but currently I don't agree > fully with "huge amounts of data". The problem was reduced immensely by > spreading writes across all free sectors rather than sequentially but I > believe? the problem re-appears on a busy nearly full disk. I would also > hope/imagine the only affect would be getting bad sectors in that area > but I haven't looked into it very far as I currently have no need to > and so maybe I should shut up untill I do. However, I for one will not > be treating SSDs like HDDs in all applications of disks untill after I > learn more. >
Just for the record, the sandforce controller used by the mentioned SSD drives keeps 6% or 25% (depending on version) for internal consumption and write wear leveling logic. So a 100GB OCZ drive is internally a 128GB one and the drive will do a lot of magic to limit the number of writes to the SSD. The sandforce controller is very different form any other device I know. Most controllers like the samsung and intel one use a small SDRAM as cache and when the cache (normaly 64 or 128MB) is full the disk starts to behave badly. Now the sandforce does not have a cache but uses the unallocated memory for such tasks by doing that and a few other magical tricks they claim a write amplification below 1. Modern SSDs are fairly reliable like HDDs and in the end both will die and they will die in the most unpleasent way and at the worst time you can imagine. So be prepared :) -- :wq Claudio
