On Tue, 31 Mar 2020 13:01:09 -0400 Eli V <eliventer@xxxxxxxxx> wrote: > Another option is to put the 12TB drives in an mdadm RAID, and then > use the mdadm raid & the ssd for btrfs RAID1 metadata, with SINGLE > data on the the array. Currently, this will make roughly half of the > meta data lookups run at SSD speed, but there is a pending patch to > allow all the metadata reads to go to the SSD. This option is, of > course, only useful for speeding up metadata operations. It can make > large btrfs filesystems feel much more responsive in interactive use > however. If you're not taking advantage of Btrfs-side features for RAID, then might as well run LVM Cache on top of mdadm, and then Btrfs on top of the cached LV. https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/logical_volume_manager_administration/lvm_cache_volume_creation https://lukas.zapletalovi.com/2019/05/lvm-cache-in-six-easy-steps.html Or Bcache, which is the same concept, but I do not suggest it over LVM cache due to perceived lower code quality, i.e. many data loss bugs, at least in the past. And as the 2nd article mentions, you can't un-bcache a block device, even if the cache device is disabled, the metadata cannot be removed. Unlike LVM where it is easy to switch back an LV to a plain uncached one. -- With respect, Roman
