I'm trying to maximize emphemeral Windows 7 32-bit performance with CEPH's RBD as back-end storage engine. (I'm not worried about data loss, as these VMs are all ephemeral, but I am worried about performance and responsiveness of the VMs.) My questions are:
1) Are there any recommendations or best-practices on the CEPH RBD cache settings? I don't fully understand how the above parameters come into play? Can someone provide some clarification, perhaps through a quick-and-dirty scenario example?
The defaults seem low. So, I'm thinking of setting the RBD cache size to something like 1 GB, the cache max dirty to 1 GB, the cache target dirty to 500 MB, and the cache max dirty age to say 30 seconds.
2) What do people thinking of my using a separate pool of replication factor 1 for the "copy-on-write" portion of the clones of these *ephemeral* VMs? Would this further improve performance for these *ephemeral* Windows VMs?
3) In addition to #2, what if I made this addition pool (of replication factor 1) reside on the host node's RAM (ramdisk)? Pros/cons to this idea? (I'm hoping this would minimize impact of boot storms and also improve overall responsiveness.)
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