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. 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
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
kind regards
Ronny Aasen
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