maurice put forth on 2/8/2011 11:37 AM: > On 2/7/2011 1:07 PM, Roberto Spadim wrote: >> hi guys, could md send TRIM command to ssd? using ext4 discart mount option? >> if i mix ssd and hd, could this TRIM be rewrite to non TRIM compatible disks? >> > I have read that using md with SSDs is not a great idea: > Form the Fedora 14 documentation: Using any RAID level but pure striping with SSDs is a bad idea, for the exact reason in that documentation: excessive writes. SSD - Solid State Drive Note the first two words. Solid state device = integrated circuit. ICs, including those comprised of flash memory transistors, have totally different failure modes than spinning rust disks, SRDs, or "plain old mechanical hard drives". RAID'ing SSDs with any data duplicative RAID level, any mirroring or parity RAID levels, _decreases_ the life of all SSDs in the array. This is the opposite effect of what you want: reliability and lifespan. People have a misconception that SSDs are like hard disks. The only thing they have in common is that both store data and they can have a similar interface (SATA). The similarities end there. RAID is not a proper method of extending the life of SSD storage nor protecting the data on SSD devices. If you want to pool all the capacity of multiple SSDs into a single logical device, use RAID 0 or spanning, _not_ a mirror or parity RAID level. If you want to protect the data, snap it to a single large SATA drive, or a D2D backup array, and then to tape. -- Stan -- 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
