Hello,

This is a bit off-topic but still applies to the general HCI cockpit config and its for lack of better words minimal documentation.  Here is what I'm struggling to understand re: brick/volume configuration, I hope someone can perhaps point me in the right direction.  

So as I mentioned before I have three physical nodes.  Each of these have a raided boot drive for oVirt install and two additional 2TB SSD disks in JBOD.  The two SSDs are what I intend to use for glusterFS and are represented on each physical machine as /dev/sda and /dev/sdb

In my first screenshot attached gluster-default it shows the default cockpit gdeploy brick configuration screen.  Here you see that I am selecting JBOD.  The other two options for stripe size and disk count from my understanding of the documentation do not apply to JBOD and when JBOD is selected these values are ignored. 

Now the confusing part, below under the "brick configuration" section.  You will see the default here is to show the three volumes (configured on the previous step of the wizard) and have a default size set and device set as "sdb".  If I were to leave this config in place then only one single disk in each of my physical machines i.e. /dev/sdb would be used in the gluster configuration (obviously not what I want).   So to make use of both disks in each machine at least one of these has to have /dev/sda device specified. 

let's say I set the bricks like this:

engine - sda - 100gb
data - sdb - 1800gb
vmstore - sda - 500gb

I believe this would limit my data volume to the /dev/sdb device on each of the three physical machines but it limits me to the size of that physical device (2TB).  Does this mean that all VM data interaction only happens on one single disk in each node i.e. /dev/sdb in host0, 1 and 2?   I have 4TB usable space between the two jbod drives in each host, what if I wanted my data volume to be 3.5TB, is it possible? 

I want to make sure that all 6 drives in the three nodes are being used as I would think that the more drives = more I/O.  I don't want my data volume to only be reading and writing to three SSDs when I have 6 available.  If I use one of my 2TB drives for data and the other 2TB in each host is used only for engine and vmstore that would seem to me to be a big waste of drive space and potential I/O.  

If I'm understanding the above correctly and I cannot specify any more than 2TB for the data brick then is it possible for me to create two data volumes on the previous step and point them to the same mount.  That way I'd split VM storage to two separate volumes, some on /dev/sda drive and some on /dev/sdb (similar to my second screenshot titled "gluster-modified".

That might work but it just feels wrong.  What if the JBOD configuration were different.  What if instead of having 2 JBOD disks per node I had 4 or even 8 individual disks in each host how would you even define all the available devices for only three volumes?   You would have 8 devices but only three volumes you can specify device locations for. 

The configuration screens in cockpit gdeploy would make sense in a RAID environment where all of the disks are represented by one device location, but it doesn't make much sense in a JBOD configuration with multiple independent devices. 

Any recommendations or guidance in regards to how I should best lay out the volume and bricks for my use case would be greatly appreciated.

Thanks!

James


On Mon, Jul 30, 2018 at 5:20 AM, Sahina Bose <sabose@redhat.com> wrote:


On Sat, Jul 28, 2018 at 7:48 PM, <william.dossett@gmail.com> wrote:

Hi,

 

I have my ovirt 4.2 hci cluster up and running, but I have a probably stupid question.

 

During the setup and in the documents it defaults to setting up the engine datastore/volume, a VMstore/volume and a data/volume…


Engine volume = the Hosted Engine storage domain
vmstore volume = the storage domain hosting the OS disks for the VMs
data volume = the storage domain hosting the data disks of the VMs

This was designed such that when setting up for disaster recovery, you need to set up remote backup only for the data disks

Please let us know /contribute to improving the documentation if this was not clear

 

What is the Data volume for?  I am planning on running VMs on this so I would assume I need VMstore and that’s what I will grow on my system.  In previous installs you had the opportunity to create the ISO domain, but not now.  I can see how to create in the engine UI so that’s fine, but I am just wondering what people use the Data volume for as an example.

 

Thanks

Bill

 


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