For example, here is my confuguration:
superuser@admin:~$ ceph df
GLOBAL:
SIZE AVAIL RAW USED %RAW USED
242T 209T 20783G 8.38
POOLS:
NAME ID USED %USED MAX AVAIL OBJECTS
ec_backup-storage 4 9629G 3.88 137T 2465171
cache 5 136G 0.06 38393M 35036
block-devices 6 1953G 0.79 70202G 500060
*ec_backup-storage* - is Erasure Encoded pool, k=2, m=1 (default)
*cache* - is replicated pool consisting dedicated 12xSSDx60Gb disks,
replica size=3, used as cache tier for EC pool
*block-devices* - is replicated pool, replica size=3, using same OSD's
that inErasure Encoded pool
On*'**MAX AVAIL**'* column you can see that EC pool currently has
*137Tb* of free space, but in same time if we will write to replicated
pool there is only *70Tb, *but *both* pools are on the *same* *OSD's.
*So using EC pool saves 2**times more effective space in my case!
12.03.2015 17:50, Thomas Foster пишет:
Thank you! That helps alot.
On Mar 12, 2015 10:40 AM, "Steve Anthony" <sma...@lehigh.edu
<mailto:sma...@lehigh.edu>> wrote:
Actually, it's more like 41TB. It's a bad idea to run at near full
capacity (by default past 85%) because you need some space where
Ceph can replicate data as part of its healing process in the
event of disk or node failure. You'll get a health warning when
you exceed this ratio.
You can use erasure coding to increase the amount of data you can
store beyond 41TB, but you'll still need some replicated disk as a
caching layer in front of the erasure coded pool if you're using
RBD. See:
http://lists.ceph.com/pipermail/ceph-users-ceph.com/2013-December/036430.html
As to how much space you can save with erasure coding, that will
depend on if you're using RBD and need a cache layer and the
values you set for k and m (number of data chunks and coding
chunks). There's been some discussion on the list with regards to
choosing those values.
-Steve
On 03/12/2015 10:07 AM, Thomas Foster wrote:
I am looking into how I can maximize my space with replication,
and I am trying to understand how I can do that.
I have 145TB of space and a replication of 3 for the pool and was
thinking that the max data I can have in the cluster is ~47TB in
my cluster at one time..is that correct? Or is there a way to
get more data into the cluster with less space using erasure coding?
Any help would be greatly appreciated.
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--
Steve Anthony
LTS HPC Support Specialist
Lehigh University
sma...@lehigh.edu <mailto:sma...@lehigh.edu>
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