It's OneFS FEC protection nomenclature for our "hybrid" protection polices. More generally, it's written as:
N+M/b
where "N" is the number of data stripe units in a stripe, "M" is the number of FEC stripe units in a stripe, and "b" is the number of stripe units in a stripe which are allowed to reside on the same node.
For the hybrid protection policy of +2:1 (or +2d:1n in OneFS 7.2+), you have
N+2/2
where "N" varies, up to our maximum stripe width, based on cluster size. For a 3 node cluster, N=4. So your 4+2/2 says you have a 3 node cluster, and each stripe of a file can have (at most) 4 data stripe units, 2 FEC stripe units, with at most 2 stripe units, per stripe, per node. This protection policy can sustain the failure of a single node or the failure of 2 drives.
kipcranford
125 Posts
1
February 3rd, 2015 06:00
It's OneFS FEC protection nomenclature for our "hybrid" protection polices. More generally, it's written as:
N+M/b
where "N" is the number of data stripe units in a stripe, "M" is the number of FEC stripe units in a stripe, and "b" is the number of stripe units in a stripe which are allowed to reside on the same node.
For the hybrid protection policy of +2:1 (or +2d:1n in OneFS 7.2+), you have
N+2/2
where "N" varies, up to our maximum stripe width, based on cluster size. For a 3 node cluster, N=4. So your 4+2/2 says you have a 3 node cluster, and each stripe of a file can have (at most) 4 data stripe units, 2 FEC stripe units, with at most 2 stripe units, per stripe, per node. This protection policy can sustain the failure of a single node or the failure of 2 drives.
ayas
Community Manager
•
7.3K Posts
0
February 3rd, 2015 16:00
Hi kipcranford!
Perfect explanation ! Thank you very much !
Aya