On Mon, Oct 12, 2009 at 8:22 AM, Mike Snitzer <snitzer@xxxxxxxxx> wrote: > On Sun, Oct 4, 2009 at 3:40 PM, Chris Worley <worleys@xxxxxxxxx> wrote: >> When you mirror two devices, they may not have the same performance. >> For example, if one device is local and the other remote. >> >> There's nothing you can do about writes, as everything needs written. >> >> But, reads shouldn't be split 50/50: they should be balanced depending >> relative performance of each mirror to optimize overall read >> performance. > > And MD already has the ability to flag the slow paths as write-mostly, see: > > mdadm ... --write-mostly > > There is also '--write-behind' support for devices that have been > tagged as 'write-mostly'. Will "write-mostly" optimize the "read", such that both devices will be accessed in proportion to their performance? The man page says: "...and means that the ’md’ driver will avoid reading from these devices if at all possible." Even a slow device can take some of the load and increase performance. Thanks, Chris -- 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
