Chris Murphy writes: > A > > HDD1+SSD1=> > Btrfs raid1 profile for metadata, raid0 or > raid1 profile for data depending on your risk tolerance > HDD2+SSD2=> But then sometimes reads will go to one leg and miss the cache and have to hit the HDD even though the data is in the ssd cache of the other leg already. Therefore, wouldn't it be preferable to keep the mirroring underneath the cache? Also having a separate B with the other two HDDs and using it purely as a backup further halves your storage capacity ( so now only 1/4th ). Also if one disk gets spun up to satisfy a read, the next read might go start up the other disk rather than go to the one that is already running. I'd say make a raid5 of the 4 HDDs, a raid1 of the the two SSDs, and use the combined SSDs to cache the combined HDDs.
