Bug #11840
Updated by Kefu Chai almost 9 years ago
> there are three pool in ceph cluster, e.g, t1, t2 t3, and t2 is a cache of t1. > 1, we can set t1 as a cache of t2 too, then t1 is the cache of t2, t2 also is the cache of t1,a loop of cache generated; > 2, we can also set t3 as a cache of t2 ort t1, then a three level cache tier generated, t3 is the cache of t2, t2 is the cache of t1. > cache loop, and three level cache are weird, also maybe reduce the IO performance, so it'd be better to avoid complicated tier like them. > we don't support multiple tiering, so we'd better fail a "ceph osd tier add" command which intent to add a tier for another tier.