On 02/02/12 17:01, William Warren wrote: > On 2/2/2012 2:15 PM, Peter A wrote: >> If you're worried about io reliability, then buy a (way more expensive) >> SLC drive, rather than the consumer level MLC... We have some SLC drives >> here that from their manufacturer have been rated at 3 or more years of >> 100% write 24x7... >> >> Peter. >> >> _______________________________________________ >> CentOS mailing list >> CentOS at centos.org >> http://lists.centos.org/mailman/listinfo/centos > exactly hence why i said stay with OCZ or Intel..MLC drives are the > best. But also the smaller the process node the shorter the lifespan of > the flash. MLC drives will also over provision more spare flash area > most times. Aeh... that's exactly the opposite of what I said. MLC (multi level cell) SSDs store more than one bit per cell. In current devices that's mostly 2 bits per cell, but more is around the corner. On an SLC (single level cell) there is only one bit per cell - true binary just like what we have in RAM and others. SLC devices are superior in reliability because it simply takes a lot more disturbing of a cell to make it lose enough charge that a 1 gets interpreted as a 0. The devices are also usually faster, especially on a re-write basis. A Oracle 96GB flash card (SLC) physically has 128GB. Most consumer MLC devices with 128GB are sold as 120GB visible... Again in favor of the SLC. Only problem is that you pay for what you get. SLC devices are significantly more expensive. Fusion I/O and all the other server ssd vendors do the same - they give you a cheap MLC device with limited performance and reliability and a high end, much more pricey SLC unit. Peter.