it can be used for badblock reallocation if harddisk have it a harddisk is near to NOR ssd with variable accesstime, if head is near sector to be read/write accesstime is small, if sector is far from head, access time increase (normaly <=1 disk revolution if head control system is good, for 7200rpm 1revolution is near to 8.33ms) 2011/2/21 Mathias Burén <mathias.buren@xxxxxxxxx>: > On 22 February 2011 01:46, Roberto Spadim <roberto@xxxxxxxxxxxxx> wrote: >> if it make sense on ssd, harddisk make sense too, it's a block device >> like ssd, the diference of ssd/harddisk? access time, >> bytes(bits)/block, life time >> bad block exist in ssd and harddisk, ssd can realloc online, some harddisks too >> >>> no, because the host may immediately write to a trim'd sector >> yes, filesystem know where exists a unused sector >> if device (harddisk/ssd) know and have a reallocation algorithm, it >> can realloc without telling filesystem to do it (that's why TRIM is >> interesting) >> since today ssd use NAND (not NOR) the block size isn't 1 bit like a >> harddisk head. trim for harddisk only make sense for badblock >> reallocation >> -------------------------- >> getting back to the first question, can MD support trim? yes/no/not >> now/some levels and layouts only? >> -- >> Roberto Spadim >> Spadim Technology / SPAEmpresarial > > This explains a bit why trim is good for SSDs and has nothing to do > with harddrives at all, since they use spinning platters and not > chips. http://www.anandtech.com/show/2738/10 > > // Mathias > -- > 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
