Op 13 aug. 2016 om 03:19 heeft Bill Sharer het volgende geschreven:
If all the system disk does is handle the o/s (ie osd journals are
on dedicated or osd drives as well), no problem. Just rebuild the
system and copy the ceph.conf back in when you re-install ceph.Â
Keep a spare copy of your original fstab to keep your osd filesystem
mounts straight.
With systems deployed with ceph-disk/ceph-deploy you no longer need a
fstab. Udev handles it.
Just keep in mind that you are down 11 osds while that system drive
gets rebuilt though. It's safer to do 10 osds and then have a
mirror set for the system disk.
In the years that I run Ceph I rarely see OS disks fail. Why bother?
Ceph is designed for failure.
I would not sacrifice a OSD slot for a OS disk. Also, let's say a
additional OS disk is €100.
If you put that disk in 20 machines that's €2.000. For that money
you can even buy a additional chassis.
No, I would run on a single OS disk. It fails? Let it fail.
Re-install
and you're good again.
Ceph makes sure the data is safe.
Wido,
can you elaborate a little bit more on this? How does CEPH achieve
that? Is it by redundant MONs?
To my understanding the OSD mapping is needed to have the cluster back.
In our setup (I assume in others as well) that is stored in the OS
disk.Furthermore, our MONs are running on the same host as OSDs. So if
the OS disk fails not only we loose the OSD host but we also loose the
MON node. Is there another way to be protected by such a failure besides
additional MONs?
We recently had a problem where a user accidentally deleted a volume.
Of course this has nothing to do with OS disk failure itself but we 've
been in the loop to start looking for other possible failures on our
system that could jeopardize data and this thread got my attention.
Warmest regards,
George
Wido
Bill Sharer
On 08/12/2016 03:33 PM, Ronny Aasen wrote:
On 12.08.2016 13:41, Félix Barbeira wrote:
Hi,
I'm planning to make a ceph cluster but I have a serious doubt. At
this moment we have ~10 servers DELL R730xd with 12x4TB SATA
disks. The official ceph docs says:
"We recommend using a dedicated drive for the operating system and
software, and one drive for each Ceph OSD Daemon you run on the
host."
I could use for example 1 disk for the OS and 11 for OSD data. In
the operating system I would run 11 daemons to control the OSDs.
But...what happen to the cluster if the disk with the OS fails??
maybe the cluster thinks that 11 OSD failed and try to replicate
all that data over the cluster...that sounds no good.
Should I use 2 disks for the OS making a RAID1? in this case I'm
"wasting" 8TB only for ~10GB that the OS needs.
In all the docs that i've been reading says ceph has no unique
single point of failure, so I think that this scenario must have a
optimal solution, maybe somebody could help me.
Thanks in advance.
--
Félix Barbeira.
if you do not have dedicated slots on the back for OS disks, then i
would recomend using SATADOM flash modules directly into a SATA port
internal in the machine. Saves you 2 slots for osd's and they are
quite reliable. you could even use 2 sd cards if your machine have
the internal SD slot
http://www.dell.com/downloads/global/products/pedge/en/poweredge-idsdm-whitepaper-en.pdf
[1]
kind regards
Ronny Aasen
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