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Petersen wrote:=0A= > =0A= > Damien,=0A= > =0A= >> With the single LUN approach, the fault domain does not really change=0A= >> from a regular device. The typical use in case of bad heads would be=0A= >> to replace the drive or reformat it at lower capacity with head=0A= >> depop. That could be avoided with dm-linear on top (one DM per=0A= >> actuator) though.=0A= > =0A= > I was more thinking along the lines of btrfs making sure to place=0A= > dup metadata on different actuators or similar.=0A= > =0A= >> The above point led me to this informational only implementation.=0A= >> Without optimization, we get the same as today. No changes in=0A= >> performance and use. Better IOPS is gain for lucky workloads=0A= >> (typically random ones). Going forward, more reliable IOPS &=0A= >> throughput gains are possible with some additional changes.=0A= > =0A= > Sure, but that means the ranges need to affect both I/O scheduling and=0A= > data placement. We need to make sure that the data placement interface=0A= > semantics are applicable to other types of media than multi actuator=0A= > drives. Filesystems shouldn't have to look at different queue limits if= =0A= > they sit on top of dm-linear instead of sd. From an I/O scheduling=0A= > perspective I concur that device implementation details are pertinent.=0A= =0A= Currently, FSes cannot know the dm-linear config. The queue crange interfac= e can=0A= actually unify this for split/dual actuator and dm-linear like logical disk= s.=0A= =0A= I need to send patches to dm-devel for that though as currently, dm-linear = does=0A= not expose its config as cranges. If I recall correctly, Hannes was also=0A= interested in playing with that too :)=0A= =0A= =0A= -- =0A= Damien Le Moal=0A= Western Digital Research=0A=