19 Feb
2020
19 Feb
'20
7:10 p.m.
On 2/19/20 3:17 PM, Frank R wrote:
Hi all,
I have noticed that RedHat is willing to support 2x replication with
NVME drives. Additionally, I have seen CERN presentation where they
use a 2x replication with NVME for a hyperconverged/HPC/CephFS
solution.
Don't do this if you care about your data. NVMe isn't anything better or
worse than SSDs. It's actually still an SSD, but we swapped the SATA/SAS
controller for NVMe, but it's still flash.
I would like to hear some opinions on whether this is
really a good
idea for production. Is this setup (NVME/2x replication) really only
meant to be used for data that is backed up and/or can be lost without
causing a catastrophe.
Yes.
You can still loose data due to a single drive failure or OSD crash.
Let's say you have an OSD/host down for maintenance or due to a network
outage. The OSD's device isn't lost, but it's unavailable.
While that happens you loose another OSD, but this time you actually
loose the device due to a failure.
Now you've lost data. Although you *think* you still have another OSD
which is in a healthy state. If you boot the OSD you'll find out it's
outdated because writes happened to the OSD you just lost.
Result = data loss
2x replication is a bad thing in production if you care about your data.
Wido
> Thanks,
> Frank
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