Am 06.11.2012 00:45, schrieb Josh Durgin:
On 11/05/2012 06:14 AM, Stefan Priebe - Profihost AG wrote:
Hello list,
Is there a way to change the number of pg_num / pgp_num after adding
more osds?
The pg_num/pgp_num settings are only used by mkcephfs at install time.
I mean i would like to start with 16 OSDs but i think i'll expand over
time to up to 100 OSDs. So i think i need to tune pg_num / pgp_num.
You can specify pg_num when creating a pool:
ceph osd pool create <name> <pgnum>
But you don't want to have too many (thousands per osd). Being able
to change the number of pgs in a pool (pg splitting/merging) is in
the works, but in the mean time you can create more pools after you add
a bunch of osds to keep your pg/osd ratio around 100.
Thanks Josh for your explanation. I'm not sure if i already understood
what pg is at all.
First i see that ceph is creating 832 pgs for 12 osds in my case per
default. This is 69,3333333 per OSD. You're talking about 100 - is the
default calculation broken or hardcoded?
When i have one pool with 800 pgs and i add 20 new OSDs how does a new
pool help? I mean the old pools will stay with 800 pgs.
Thanks again!
Greets,
Stefan
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