yeah, the idea of implement of TRIM at MD is to send TRIM to devices that was received by MD on filesystem level raid1 + no layout + all mirrors with TRIM support=> i think it´s easy to implement... just send the command to mirros (ssd or hd, since they support it) for striped devices?! maybe could support, it´s more dificult for linear raid0 it could be easy too 2011/2/21 Mathias Burén <mathias.buren@xxxxxxxxx>: > On 21 February 2011 19:38, Mathias Burén <mathias.buren@xxxxxxxxx> wrote: >> On 21 February 2011 19:32, Roberto Spadim <roberto@xxxxxxxxxxxxx> wrote: >>> TRIM isn´t a problem, it´s a solution to optimize dynamic allocation, >>> and life time of devices (SSD or harddisk) >>> i don´t see any problem to implement trim command on hard disks (not >>> in linux, but at harddisk firmware level) >>> >>> hard disk have the same problem of ssd, allocation of badblocks, any >>> harddisk could implement trim and use it to realloc badblocks... >>> >>> -- >>> Roberto Spadim >>> Spadim Technology / SPAEmpresarial >>> >> >> I don't think you understand TRIM. It wouldn't work, and there is no >> need for it, on a HDD. AFAIK a HDD does not have the same penalty as a >> SSD does when it needs to write to a (previously) used area. An SSD >> cannot do this without erasing the whole (block? page?), usually 512KB >> in size (varies between different manufacturers), but the data that's >> on there still needs to be moved elsewhere first, block erased, data >> moved back the same time the new data is written together with it. >> AFAIK it works something like this anyway. The only benefit TRIM will >> give you would be potentially faster writes, right. >> >> // M >> > > Plus support is needed from the kernel (done) filesystem (ext4 has > it). The filesystem seese the MD device, not the actual SSDs behind > it, so it would probably be quite complicated to implement passthrough > of the trim command in this case. > > // M > -- > 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
