On Tue, 13 May 2014 22:03:11 +1200 Mark Kirkwood wrote: > On thing that would put me off the 530 is lack on power off safety > (capacitor or similar). Given the job of the journal, I think an SSD > that has some guarantee of write integrity is crucial - so yeah the > DC3500 or DC3700 seem like the best choices. > All my machines have redundant PSUs fed from redundant circuits in very high end datacenters backed up by the usual gambit of batteries and diesel monsters. So while you (and the people who's first comment about RAID controllers is to mention that one should get a BBU) certainly have a point I'm happily deploying 530s where they are useful. If that power should ever fail, I'm most likely buried under a ton of (optionally radioactive) rubble (Tokyo here) or if I'm lucky just that one DC is flooded, in which case the data is lost as well. ^o^ My beef with the 530 is that is spiky, you can't really rely on it for consistent throughput and IOPS. Christian > Regards > > Mark > > On 13/05/14 21:31, Christian Balzer wrote: > > > > Hello, > > > > No actual question, just some food for thought and something that later > > generations can scour from the ML archive. > > > > I'm planning another Ceph storage cluster, this time a "classic" Ceph > > design, 3 storage nodes with 8 HDDs for OSDs and 4 SSDs for OS and > > journal. > > > > When juggling the budget for it the 12 DC3700 200GB SSDs of my first > > draft stood out like the proverbial sore thumb, nearly 1/6th of the > > total budget. > > I really like those SSDs with their smooth performance and durability > > of 1TB/day writes (over 5 years, same for all the other numbers > > below), but wondered if that was really needed. > > > > This cluster is supposed to provide the storage for VMs (Vservers > > really) that are currently on 3 DRBD cluster pairs. > > Not particular write intensive, all of them just total about 20GB/day. > > With 2 journals per SSD that's 5GB/day of writes, well within the Intel > > specification of 20GB/day for their 530 drives (180GB version). > > > > However the uneven IOPS of the 530 and potential future changes in > > write patterns make this 300% safety margin still to slim for my > > liking. > > > > Alas a DC3500 240GB SSD will perform well enough at half the price of > > the DC3700 and give me enough breathing room at about 80GB/day writes, > > so this is what I will order in the end. > > > > Christian > > > > -- Christian Balzer Network/Systems Engineer chibi at gol.com Global OnLine Japan/Fusion Communications http://www.gol.com/
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