On 5/4/20 16:08, Zygo Blaxell wrote: > The basic problem with DM-SMR drives is that they cache writes in CMR > zones for a while, but they need significant idle periods (no read or > write commands from the host) to move the data back to SMR zones, or > they run out of CMR space and throttle writes from the host. Does anybody know where the drive keeps all that metadata? On rotating disk, or in flash somewhere? Just wondering what happens when power suddenly fails during these rewrite operations. > > Some kinds of RAID rebuild don't provide sufficient idle time to complete > the CMR-to-SMR writeback, so the host gets throttled. If the drive slows My understanding is that large sequential writes can go directly to the SMR areas, which is an argument for a more conventional RAID array. How hard does btrfs try to do large sequential writes?
