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@xxxxxxxx> 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 > > Looking for help with your Ceph cluster? Contact us at https://croit.io > > croit GmbH > Freseniusstr. 31h > 81247 München > www.croit.io > Tel: +49 89 1896585 90 > > On Wed, Feb 19, 2020 at 4:41 PM Wido den Hollander <wido@xxxxxxxx> 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 outdated because writes happened to the OSD you just lost.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@xxxxxxx > > > To unsubscribe send an email to ceph-users-leave@xxxxxxx > > > > > _______________________________________________ > > ceph-users mailing list -- ceph-users@xxxxxxx > > To unsubscribe send an email to ceph-users-leave@xxxxxxx > _______________________________________________ > ceph-users mailing list -- ceph-users@xxxxxxx > To unsubscribe send an email to ceph-users-leave@xxxxxxx _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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