>Then again, my attitude > about this is very arrogant and I think the trim spec was broken from > the beginning. maybe... we could put all harddisk firmware at linux code... why we need reallocation of harddisks? we need when filesystem don´t do it we question is: can we implement TRIM at MD device? 2011/2/21 Doug Dumitru <doug@xxxxxxxxxx>: > To be technically accurate, trim is a hint to a storage device that > has a "block translation layer" that can take advantage of knowing > that a block contains no meaningful data. > > Flash needs trim only if flash has an FTL (Flash Translation Layer) > that is re-mapping blocks in such a manner as free blocks are helpful > in making this process more efficient. Older SSDs did not support > trim and had no real need for it. If you look at the FTL used with > simple Flash (think CF cards, SD cards, and USB sticks) trim does not > help them. Trim and wear leveling are un-related and don't really > impact each other. > > On the linux side trim is "discard". This is actually a much better > abstraction as it does not imply SSDs. > > Any type of block device that does dynamic block remapping will likely > be helped (at least somewhat) by discard. The only examples of this I > can think of off-hand are 1) my Flash SuperCharger code, and 2) > block-level de-dupe engines. I am sure other examples will be created > over time. > > Hopefully, discard can be driven down the stack. I would personally > prefer the linux community declare that discard and zero writes are > identical. If an SSD supports trim and linux wants to translate a > discard into a trim at the device driver layer, and the SSD is > non-deterministic, then that SSD is broken. Then again, my attitude > about this is very arrogant and I think the trim spec was broken from > the beginning. > > -- > Doug Dumitru > EasyCo LLC > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Roberto Spadim Spadim Technology / SPAEmpresarial -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
