Network optimization for ceph.

[alexskysilk]

does the device class makes a difference ?

In two ways-
1. ceph deploys different tunable values depending on device class
2. In case of a variety of OSD types, if you do NOT specify a class the data will be written to all available disks- and you wont get any benefit from the faster disk classes.

 

[plastilin]

In two ways-
1. ceph deploys different tunable values depending on device class
2. In case of a variety of OSD types, if you do NOT specify a class the data will be written to all available disks- and you wont get any benefit from the faster disk classes.

Can you clarify how the process of writing and reading on the OSD. From the official documentation, you can see the logic that exactly 1 OSD is used and not a group of OSD disks. That is, in fact, it writes to a specific OSD and then replicates to another OSD 2 nodes and also replicates to OSD 3 nodes, after which the client confirms the write. This would then explain the low write speed, which is +- equal to the write speed of a single disc.

 

[alexskysilk]

you can see the logic that exactly 1 OSD is used and not a group of OSD disks.

see the final acknowledgement? you have to wait till all writes were completed and acknowledge before the write is acknowledged to the requestor.