Re: Adding multiple OSD

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Thank you for detailed explanation!

Got one another doubt, 

This is the total space available in the cluster : 

TOTAL 23490G 
Use 10170G 
Avail : 13320G 


But ecpool shows max avail as just 3 TB. 



Karun Josy

On Tue, Dec 5, 2017 at 1:06 AM, David Turner <drakonstein@xxxxxxxxx> wrote:
No, I would only add disks to 1 failure domain at a time.  So in your situation where you're adding 2 more disks to each node, I would recommend adding the 2 disks into 1 node at a time.  Your failure domain is the crush-failure-domain=host.  So you can lose a host and only lose 1 copy of the data.  If all of your pools are using the k=5 m=3 profile, then I would say it's fine to add the disks into 2 nodes at a time.  If you have any replica pools for RGW metadata or anything, then I would stick with the 1 host at a time.

On Mon, Dec 4, 2017 at 2:29 PM Karun Josy <karunjosy1@xxxxxxxxx> wrote:
Thanks for your reply!

I am using erasure coded profile with k=5, m=3 settings

$ ceph osd erasure-code-profile get profile5by3
crush-device-class=
crush-failure-domain=host
crush-root=default
jerasure-per-chunk-alignment=false
k=5
m=3
plugin=jerasure
technique=reed_sol_van
w=8


Cluster has 8 nodes, with 3 disks each. We are planning to add 2 more on each nodes.

If I understand correctly, then I can add 3 disks at once right , assuming 3 disks can fail at a time as per the ec code profile. 

Karun Josy

On Tue, Dec 5, 2017 at 12:06 AM, David Turner <drakonstein@xxxxxxxxx> wrote:
Depending on how well you burn-in/test your new disks, I like to only add 1 failure domain of disks at a time in case you have bad disks that you're adding.  If you are confident that your disks aren't likely to fail during the backfilling, then you can go with more.  I just added 8 servers (16 OSDs each) to a cluster with 15 servers (16 OSDs each) all at the same time, but we spent 2 weeks testing the hardware before adding the new nodes to the cluster.

If you add 1 failure domain at a time, then any DoA disks in the new nodes will only be able to fail with 1 copy of your data instead of across multiple nodes.

On Mon, Dec 4, 2017 at 12:54 PM Karun Josy <karunjosy1@xxxxxxxxx> wrote:
Hi,

Is it recommended to add OSD disks one by one or can I add couple of disks at a time ?

Current cluster size is about 4 TB.



Karun 
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