Hi

I just thought that you'd do hardware RAID if you had the controller or JBOD if you didn't.  In hindsight, a server with 40Gbps NICs is pretty likely to have a hardware RAID controller.  I've never done JBOD with hardware RAID.  I think having a single gluster brick on hardware JBOD would be riskier than multiple bricks, each on a single disk, but thats not based on anything other than my prejudices.

I thought gluster tiering was for the most frequently accessed files, in which case all the VMs disks would end up in the hot tier.  However, I have been wrong before...

I just wanted to know where the OS was going as I didn't see it mentioned in the OP.  Normally, I'd have the OS on a RAID1 but in your case thats a lot of wasted disk.

Honestly, I think Yaniv's answer was far better than my own and made the important point about having an arbiter. 

Thanks

On Mon, Aug 7, 2017 at 5:56 PM, Moacir Ferreira <moacirferreira@hotmail.com> wrote:

Hi Colin,

I am in Portugal, so sorry for this late response. It is quite confusing for me, please consider:

1 - What if the RAID is done by the server's disk controller, not by software?

2 - For JBOD I am just using gdeploy to deploy it. However, I am not using the oVirt node GUI to do this.

3 - As the VM .qcow2 files are quite big, tiering would only help if made by an intelligent system that uses SSD for chunks of data not for the entire .qcow2 file. But I guess this is a problem everybody else has. So, Do you know how tiering works in Gluster?

4 - I am putting the OS on the first disk. However, would you do differently?

Moacir

---

From: Colin Coe <colin.coe@gmail.com>
Sent: Monday, August 7, 2017 4:48 AM
To: Moacir Ferreira
Cc: users@ovirt.org
Subject: Re: [ovirt-users] Good practices

 

1) RAID5 may be a performance hit-

2) I'd be inclined to do this as JBOD by creating a distributed disperse volume on each server.  Something like

echo gluster volume create dispersevol disperse-data 5 redundancy 2 \

$(for SERVER in a b c; do for BRICK in $(seq 1 5); do echo -e "server${SERVER}:/brick/brick-${SERVER}${BRICK}/brick \c"; done; done)

3) I think the above.

4) Gluster does support tiering, but IIRC you'd need the same number of SSD as spindle drives.  There may be another way to use the SSD as a fast cache. 

Where are you putting the OS?

Hope I understood the question...

Thanks

On Sun, Aug 6, 2017 at 10:49 PM, Moacir Ferreira <moacirferreira@hotmail.com> wrote:

I am willing to assemble a oVirt "pod", made of 3 servers, each with 2 CPU sockets of 12 cores, 256GB RAM, 7 HDD 10K, 1 SSD. The idea is to use GlusterFS to provide HA for the VMs. The 3 servers have a dual 40Gb NIC and a dual 10Gb NIC. So my intention is to create a loop like a server triangle using the 40Gb NICs for virtualization files (VMs .qcow2) access and to move VMs around the pod (east /west traffic) while using the 10Gb interfaces for giving services to the outside world (north/south traffic).

This said, my first question is: How should I deploy GlusterFS in such oVirt scenario? My questions are:

1 - Should I create 3 RAID (i.e.: RAID 5), one on each oVirt node, and then create a GlusterFS using them?

2 - Instead, should I create a JBOD array made of all server's disks?

3 - What is the best Gluster configuration to provide for HA while not consuming too much disk space?

4 - Does a oVirt hypervisor pod like I am planning to build, and the virtualization environment, benefits from tiering when using a SSD disk? And yes, will Gluster do it by default or I have to configure it to do so?

At the bottom line, what is the good practice for using GlusterFS in small pods for enterprises?

You opinion/feedback will be really appreciated!

Moacir

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