I'm looking to improve the raw performance on my small setup (2 Compute Nodes, 2 OSD's). Only used for hosting KVM images. Raw read/write is roughly 200/35 MB/s. Starting 4+ VM's simultaneously pushes iowaits over 30%, though the system keeps chugging along. Budget is limited ... :( I plan to upgrade my SSD journals to something better than the Samsung 840 EVO's (Intel 520/530?) One of the things I see mentioned a lot in blogs etc is how ceph's performance improves as you add more OSD's and that the quality of the disks does not matter so much as the quantity. How does this work? does ceph stripe reads and writes across the OSD's to improve performance? If I add 3 cheap OSD's to each node (500GB - 1TB) with 10GB SSD journal partition each could I expect a big improvement in performance? What sort of redundancy to setup? currently its min= 1, size=2. Size is not an issue, we already have 150% more space than we need, redundancy and performance is more important. Now I think on it, we can live with the slow write performance, but reducing iowait would be *really* good. thanks, -- Lindsay
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