Re: Squeezing Performance of CEPH

[Ashley Merrick <ashley@xxxxxxxxxxxxxx>]

You could move your Journal to another SSD this would remove the double write. Ideally you’d want one or two PCIe NVME in the servers for the Journal.

Or if you can hold off a bit then bluestore, which removes the double write, however is still handy to move some of the services to a seperate disk.

,Ashley

Sent from my iPhone

On 23 Jun 2017, at 7:45 PM, Massimiliano Cuttini <max@xxxxxxxxxxxxx> wrote:

Of course yes!

SSD bottleneck is the SATA controller.
If you use a NVMe/PCIe controller you get from almost the same SSD 2.400MB/sec instead of 580MB/sec.

2400MB/sec x 8 =  ~19Gbit/sec
580MB/sec x 8 = ~5 Gbit/sec

If you don't trust me take a look at this benchmark between 2 really common SSD in the consumer market:
http://ssd.userbenchmark.com/Compare/Samsung-960-Pro-NVMe-PCIe-M2-512GB-vs-Samsung-850-Pro-256GB/m182182vs2385

So of course, talking about SSD, your speed is grossy the SATA controller (minus the overhead of the protocol).

Il 22/06/2017 20:35, ceph@xxxxxxxxxxxxxx ha scritto:

On 22/06/2017 19:19, Massimiliano Cuttini wrote:

We are already expecting the following bottlenecks:

 * [ SATA speed x n° disks ] = 24Gbit/s
 * [ Networks speed x n° bonded cards ] = 200Gbit/s

6Gbps SATA does not mean you can read 6Gbps from that device

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