Hello, On Tue, 06 May 2014 17:07:33 +0200 Xabier Elkano wrote: > > Hi, > > I'm designing a new ceph pool with new hardware and I would like to > receive some suggestion. > I want to use a replica count of 3 in the pool and the idea is to buy 3 > new servers with a 10-drive 2,5" chassis each and 2 10Gbps nics. I have > in mind two configurations: > As Wido said, more nodes are usually better, unless you're quite aware of what you're doing and why. > 1- With journal in SSDs > > OS: 2xSSD intel SC3500 100G Raid 1 > Journal: 2xSSD intel SC3700 100G, 3 journal for each SSD As I wrote just a moment ago, use at least the 200GB ones if performance is such an issue for you. If you can afford it, use 4 3700s and share OS and journal, the OS IOPS will not be that significant, especially if you're using a writeback cache controller. > OSD: 6 SAS10K 900G (SAS2 6Gbps), each running an OSD process. Total size > for OSDs: 5,4TB > > 2- With journal in a partition in the spinners. > > OS: 2xSSD intel SC3500 100G Raid 1 > OSD+journal: 8 SAS15K 600G (SAS3 12Gbps), each runing an OSD process and > its journal. Total size for OSDs: 3,6TB > I have no idea why anybody would spend money on 12Gb/s HDDs when even most SSDs have trouble saturating a 6Gb/s link. Given the double write penalty in IOPS, I think you're going to find this more expensive (per byte) and slower than a well rounded option 1. > The budget in both configuration is similar, but the total capacity not. > What would be the best configuration from the point of view of > performance? In the second configuration I know the controller write > back cache could be very critical, the servers has a LSI 3108 controller > with 2GB Cache. I have to plan this storage as a KVM image backend and > the goal is the performance over the capacity. > Writeback cache can be very helpful, however it is not a miracle cure. Not knowing your actual load and I/O patterns it might very well be enough, though. Regards, Christian -- Christian Balzer Network/Systems Engineer chibi at gol.com Global OnLine Japan/Fusion Communications http://www.gol.com/
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