And btw EC with k=2, m=2, min_size=3, is also probably fine, and has only x2 space cost. -- dan On Wed, Feb 19, 2020 at 5:46 PM Paul Emmerich <paul.emmerich@croit.io> wrote:
x2 replication is perfectly fine as long as you also keep min_size at 2 ;)
(But that means you're offline as soon as something is offline)
Paul
-- Paul Emmerich
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On Wed, Feb 19, 2020 at 4:41 PM Wido den Hollander <wido@42on.com> wrote:
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 If you boot the OSD you'll find out it's outdated because writes happened to the OSD you just lost.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 _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io
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