On Mon, May 04 2015 at 6:37am -0400, Akira Hayakawa <ruby.wktk@xxxxxxxxx> wrote: > Hi, > > Some DM target requires additional device that could be a single point of failure. > Let's consider dm-cache. > dm-cache requires a HDD and a SSD and if SSD is dead, the data is lost. > To protect from this, SSD can be built RAID. But RAID isn't an ideal solution with SSD > because the devices can be dead at the same time. Cost is the another problem of course. > > So, let's think about hotswap. > A hotswap device has an active device and multiple ready devices. > The active device is usually used and when the device is ordered to swap by > a ready device it starts to sync the two devices and change the active device > when sync is over. It's not simply dd-ing the devices because I/O isn't suspended and > not all region is necessarily copied. > You can order swapping whenever you like to. For example, swapping every week can be > double the longevity of the cache device. > > I don't know how I can do this with DM targets. > Do other part of linux technologies have such functinality? Please teach me if so. You could probably use lvm2's pvmove (it uses old dm-mirror target to swap over). -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
