Nobody explains why, I will tell you from direct experience: the cache tier
has a block size of several megabytes. So if you ask for one byte that is
not in cache some megabytes are read from disk and, if cache is full, some
other megabytes are written from cache to the EC pool.
Il giorno gio 28
Hello David,
Thank you!
We setup 2 pools to use EC with RBD. One ecpool and other normal replicated
pool.
However, would it still be advantageous to add a replicated cache tier in
front of an EC one, even though it is not required anymore? I would still
assume that replication would be less
Also carefully read the word of caution section on David's link (which is
absent in the jewel version of the docs), a cache tier in front of an ersure
coded data pool for RBD is almost always a bad idea.
I would say that statement is incorrect if using Bluestore. If using Bluestore,
Also carefully read the word of caution section on David's link (which is
absent in the jewel version of the docs), a cache tier in front of an
ersure coded data pool for RBD is almost always a bad idea.
Caspar
Met vriendelijke groet,
Caspar Smit
Systemengineer
SuperNAS
Dorsvlegelstraat 13
1445
Please use the version of the docs for your installed version of ceph. Now
the Jewel in your URL and the Luminous in mine. In Luminous you no longer
need a cache tier to use EC with RBDs.
http://docs.ceph.com/docs/luminous/rados/operations/cache-tiering/
On Tue, Dec 26, 2017, 4:21 PM Karun
Hi,
We are using Erasure coded pools in a ceph cluster for RBD images.
Ceph version is 12.2.2 Luminous.
-
http://docs.ceph.com/docs/jewel/rados/operations/cache-tiering/
-
Here it says we can use a Cache tiering infront of ec pools.
To use erasure code with RBD we have a replicated
