write performance per disk

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Hi,

I have a ceph cluster setup (with 45 sata disk journal on disks) and get only 450mb/sec writes seq (maximum playing around with threads in rados bench) with replica of 2
Which is about ~20Mb writes per disk (what y see in atop also)
theoretically with replica2 and having journals on disk should be 45 X 100mb (sata) / 2 (replica) / 2 (journal writes) which makes it 1125
satas in reality have 120mb/sec so the theoretical output should be more.

I would expect to have between 40-50mb/sec for each sata disk

Can somebody confirm that he can reach this speed with a setup with journals on the satas (with journals on ssd speed should be 100mb per disk)?
or does ceph only give about ? of the speed for a disk? (and not the ? as expected because of journals)


My setup is 3 servers with: 2 x 2.6ghz xeons, 128gb ram 15 satas for ceph (and ssds for system) 1 x 10gig for external traffic, 1 x 10gig for osd traffic
with reads I can saturate the network but writes is far away. And I would expect at least to saturate the 10gig with sequential writes also

Thank you
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