Do you feel that SSDs are worth the extra cost or am I better off using regular HDDs?  I'm looking for the best performance I can get with glusterFS

On Fri, Mar 23, 2018 at 12:03 AM, Manoj Pillai <mpillai@redhat.com> wrote:

On Thu, Mar 22, 2018 at 3:31 PM, Sahina Bose <sabose@redhat.com> wrote:

On Mon, Mar 19, 2018 at 5:57 PM, Jayme <jaymef@gmail.com> wrote:

I'm spec'ing a new oVirt build using three Dell R720's w/ 256GB.  I'm considering storage options.  I don't have a requirement for high amounts of storage, I have a little over 1TB to store but want some overhead so I'm thinking 2TB of usable space would be sufficient. 

I've been doing some research on Micron 1100 2TB ssd's and they seem to offer a lot of value for the money.  I'm considering using smaller cheaper SSDs for boot drives and using one 2TB micron SSD in each host for a glusterFS replica 3 setup (on the fence about using an arbiter, I like the extra redundancy replicate 3 will give me).

My question is, would I see a performance hit using only one drive in each host with glusterFS or should I try to add more physical disks.  Such as 6 1TB drives instead of 3 2TB drives? 

It is possible. With SSDs the rpc layer can become the bottleneck with some workloads, especially if there are not enough connections out to the server side. We had experimented with a multi-connection model for this reason:  https://review.gluster.org/#/c/19133/.

-- Manoj

[Adding gluster-users for inputs here]

Also one other question.  I've read that gluster can only be done in groups of three.  Meaning you need 3, 6, or 9 hosts.  Is this true?  If I had an operational replicate 3 glusterFS setup and wanted to add more capacity I would have to add 3 more hosts, or is it possible for me to add a 4th host in to the mix for extra processing power down the road?

In oVirt, we support replica 3 or replica 3 with arbiter (where one of the 3 bricks is a low storage arbiter brick). To expand storage, you would need to add in multiples of 3 bricks. However if you only want to expand compute capacity in your HC environment, you can add a 4th node.

Thanks!

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