Re: Designing ceph cluster

[Mart van Santen <mart@xxxxxxxxxxxx>]

Dear Guarav,

Please respect everyones time & timezone differences. Flooding the mail-list won't help

see below,

On 08/18/2016 01:39 AM, Gaurav Goyal wrote:

Dear Ceph Users,

Awaiting some suggestion please!

On Wed, Aug 17, 2016 at 11:15 AM, Gaurav Goyal <er.gauravgoyal@xxxxxxxxx> wrote:

Hello Mart,

Thanks a lot for the detailed information!

Please find my response inline and help me to get more knowledge on it

Ceph works best with more hardware. It is not really designed for small scale setups. Of course small setups can work for a PoC or testing, but I would not advise this for production.

[Gaurav] : We need this setup for PoC or testing. 

If you want to proceed however, have a good look the manuals or this mailinglist archive and do invest some time to understand the logic and workings of ceph before working or ordering hardware

At least you want: 
- 3 monitors, preferable on dedicated servers

[Gaurav] : With my current setup, can i install MON on Host 1 --> Controller + Compute1, Host 2 and Host 3

- Per disk you will be running an ceph-osd instance. So a host with 2 disks will run 2 osd instances. More OSD process is better performance, but also more memory and cpu usage.

[Gaurav] : Understood, That means having 1T x 4 would be better than 2T x 2.

Yes, more disks will do more IO

- Per default ceph uses a replication factor of 3 (it is possible to set this to 2, but is not advised)
- You can not fill up disks to 100%, also data will not distribute even over all disks, expect disks to be filled up (on average) maximum to 60-70%. You want to add more disks once you reach this limit.

All on all, with a setup of 3 hosts, with 2x2TB disks, this will result in a net data availablity of (3x2x2TBx0.6)/3 = 2.4 TB 

[Gaurav] : As this is going to be a test lab environment, can we change the configuration to have more capacity rather than redundancy? How can we achieve it?

Ceph has an excellent documentation. This is easy to find and search for "the number of replicas", you want to set both "size" and "min_size" to 1 on this case

If speed is required, consider SSD's (for data & journals, or only journals).

In you email you mention "compute1/2/3", please note, if you use the rbd kernel driver, this can interfere with the OSD process and is not advised to run OSD and Kernel driver on the same hardware. If you still want to do that, split it up using VMs (we have a small testing cluster where we do mix compute and storage, there we have the OSDs running in VMs)

[Gaurav] : within my mentioned environment, How can we split rbd kernel driver and OSD process? Should it be like rbd kernel driver on controller and OSD processes on compute hosts?

Since my host 1 is controller + Compute1, Can you please share the steps to split it up using VMs and suggested by you.

We are running kernel rbd on dom0 and osd's in domu, as well a monitor in domu.

Regards,

Mart

Regards

Gaurav Goyal 

On Wed, Aug 17, 2016 at 9:28 AM, Mart van Santen <mart@xxxxxxxxxxxx> wrote:

Dear Gaurav,

Ceph works best with more hardware. It is not really designed for small scale setups. Of course small setups can work for a PoC or testing, but I would not advise this for production.

If you want to proceed however, have a good look the manuals or this mailinglist archive and do invest some time to understand the logic and workings of ceph before working or ordering hardware

At least you want:
- 3 monitors, preferable on dedicated servers
- Per disk you will be running an ceph-osd instance. So a host with 2 disks will run 2 osd instances. More OSD process is better performance, but also more memory and cpu usage.
- Per default ceph uses a replication factor of 3 (it is possible to set this to 2, but is not advised)
- You can not fill up disks to 100%, also data will not distribute even over all disks, expect disks to be filled up (on average) maximum to 60-70%. You want to add more disks once you reach this limit.

All on all, with a setup of 3 hosts, with 2x2TB disks, this will result in a net data availablity of (3x2x2TBx0.6)/3 = 2.4 TB


If speed is required, consider SSD's (for data & journals, or only journals).

In you email you mention "compute1/2/3", please note, if you use the rbd kernel driver, this can interfere with the OSD process and is not advised to run OSD and Kernel driver on the same hardware. If you still want to do that, split it up using VMs (we have a small testing cluster where we do mix compute and storage, there we have the OSDs running in VMs)

Hope this helps,

regards,

mart

On 08/17/2016 02:21 PM, Gaurav Goyal wrote:

Dear Ceph Users,

I need your help to redesign my ceph storage network.

As suggested in earlier discussions, i must not use SAN storage. So we have decided to removed it.

Now we are ordering Local HDDs.

My Network would be

Host1 --> Controller + Compute1 Host 2--> Compute2 Host 3 --> Compute3

Is it right setup for ceph network? For Host1 and Host2 , we are using 1 500GB disk for OS on each host .

Should we use same size storage disks 500GB *8 for ceph environment or i can order Disks in size of 2TB for ceph cluster?

Making it

2T X 2 on Host1 2T X 2 on Host 2 2T X 2 on Host 3

12TB in total. replication factor 2 should make it 6 TB?

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