> yes SSD-Journal helps a lot (if you use the right SSDs) > What SSDs to avoid for journaling from your experience? Why?
> > > We're seeing very disappointing Ceph performance. We have 10GigE > > interconnect (as a shared public/internal network). > Which kind of CPU do you use for the OSD-hosts? > > Intel(R) Xeon(R) CPU E5-2660 v2 @ 2.20GHz FYI, we are hosting VMs on our OSD nodes, but the VMs use very small amounts of CPUs and RAM > > > We're wondering whether it makes sense to buy SSDs and put journals on > > them. But we're looking for a way to verify that this will actually > > help BEFORE we splash cash on SSDs. > I can recommend the Intel DC S3700 SSD for journaling! In the beginning > I started with different much cheaper models, but this was the wrong > decision. > What, apart from the price, made the difference? sustained read/write bandwidth? IOPS? We're considering this one (PCI-e SSD). What do you think? http://www.plextor-digital.com/index.php/en/M6e-BK/m6e-bk.html PX-128M6e-BK Also, we're thinking about sharing one SSD between two OSDs. Any reason why this would be a bad idea? > > We're using Ceph for OpenStack storage (kvm). Enabling RBD cache > > didn't really help all that much. > The read speed can be optimized with an bigger read ahead cache inside > the VM, like: > echo 4096 > /sys/block/vda/queue/read_ahead_kb Thanks, we will try that.
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