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(a)redhat.com> wrote:
On Sat, Jul 28, 2018 at 7:48 PM, <william.dossett(a)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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