Hi all,
I am all new with ceph and I come from gluster.
We have had our eyes on ceph for several years
and as the gluster project seems to slow down we
now think it is time to start look into ceph.
I have manually configured a ceph cluster with ceph fs on debian
bookworm.
What is the difference from installing with cephadm compared to manuall
install,
any benefits that you miss with manual install?
There are also another couple of things that I can not figure out
reading the documentation.
Most of our files are small and from my understanding replication is
then recomended, right?
The plan is to set ceph up like this:
1 x "admin node"
2 x "storage nodes"
The admin node will run mon, mgr and mds.
The storage nodes will run mon, mgr, mds and 8x osd (8 disks).
This works well to setup but I can not get my head around is
how things are replicated over nodes and disks.
In ceth.conf I set the folowing:
osd pool default size = 2
osd pool default min size = 1
So the idea is that we always have 2 copies of the data.
I do not seem to be able to figure out the replication
when things starts to fail.
If the admin node goes down, one of the data nodes will
run the mon, mgr and mds. This will slow things down but
will be fine until we have a new admin node in place again.
(or if there is something I am missing here?)
If just one data node goes down we will still not loose any
data and that is fine until we have a new server.
But what if one data node goes down and one disk of the other
data node breaks, will I loose data then?
Or how many disks can I loose before I loose data?
This is what I can not get my head around, how to think
when disaster strikes, how much hardware can I loose before
I loose data?
Or have I got it all wrong?
Is it a bad idea with just 2 fileservers is more servers required?
The second thing I have a problem with is snapshots.
I manage to create snapshot in root with command:
ceph fs subvolume snapshot create <vol_name> / <snap_name>
But it fails if I try to create a shapshot in any
other directory then in the root.
Second of all if I try to create a snapshot from the
client with:
mkdir /mnt-ceph/.snap/my_snapshot
I get the same error in all directories:
Permission dened.
I have not found any sollution to this,
am I missing something here as well?
Any config missing?
Many thanks for your support!!
Best regrads
Marcus
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