On 10/30/2017 02:33 PM, shadow_lin wrote:
Hi all,
I am wondering how to choose the proper ec profile for new luminous ec
rbd image.
If I set the k too high what the draw back would be?
Is it a good idea to set k=10 m=2? It sounds attempting the overhead
of storage capacity is low and the redundancy is good.
Hi,
That is a consideration between how important your data is, how quickly
you think you will notice [even if Ceph somehow doesn't or can't deal
with it because of imperfect configuration or such] and how quickly you
ultimately are done rebuilding redundancy.
I'd suggest to imagine a bad scenario for how long it will take and just
consider how nervous it'd make you to be down to x OSDs/hosts of
redundancy for that duration.
Apart from that, Ceph isn't a super stable super easy to comprehend type
of software yet (no offense to anyone intended - you're overall doing a
good job!). As far as I can guess, there could be the occasional moment
when one extra copy allows you to use a simpler, more reliable "tabula
rasa" approach to host / OSD problem fixing, while staying safe enough.
shadow_lin wrote:
What is the difference for storage safety(redundancy ) between k=10
m=2 and k=4 m=2?
3 OSDs failing before you / Ceph restores them is a less likely event in
a pool of 6 than one of 12. If you had k=10 million m=2 with 12TB HDD,
it'd probably take just some seconds to minutes until you have data loss.
shadow_lin wrote:
What would be a good ec profile for archive purpose(decent write
perfomance and just ok read performace)?
I don't actually know that - but the default is not bad if you ask me
(not that it features writes faster than reads). Plus it lets you pick m.
- Michael
_______________________________________________
ceph-users mailing list
ceph-users@lists.ceph.com
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
