On 09/16/2011 09:19 PM, [email protected] wrote:
all of the chip based memory devices that are able to maintain the data without power have a limited number of write cycles. In the case of modern flash drives this is in the millions of cycles on an individual block. older flash drives wear out faster than newer ones, MLC flash drives wear out faster than SLC drives (but MLC stores two bits per cell nstead of one and has further price advantages due to volume production so it's _far_ cheaper) [...] erasing data on a flash drive is very slow, SSDs get around this by writing a new copy of the data to a new location and erasing the old copy sometime later. All modern drives contain more flash than what you pay for so that they have a large pool of 'blank' space that they can write to (this also helps spread out the writes across more flash so that you are less likely to hit the 1m write limit on any one spot). If
Sorry to barge in on this, but the write limit on modern MLC cells is much lower. For modern flash chips the MTTF is somewhere in the range of 5000 - 25000 write cycles on a cell. The rest is owed to intelligent write allocation/distribution which spreads the writes out over all the unallocated area of the disk. This is also the reason why it is so important to use the TRIM function which informs the disk about unused areas. Allowing the disk to "pre-erase" the space is just a welcome side effect. Older flash chips with larger structures have a much better MTTF. Cheers Mike _______________________________________________ Tech mailing list [email protected] https://lists.lopsa.org/cgi-bin/mailman/listinfo/tech This list provided by the League of Professional System Administrators http://lopsa.org/
