On Wed, Sep 6, 2017 at 6:08 PM, Abi Askushi <rightkicktech@gmail.com> wrote:

For a first idea I use:

dd if=/dev/zero of=testfile bs=1GB count=1

This is an incorrect way to test performance, for various reasons:

1. You are not using oflag=direct , thus not using DirectIO, but using cache.

2. It's unrealistic - it is very uncommon to write large blocks of zeros (sometimes during FS creation or wiping). Certainly not 1GB

3. It is a single thread of IO - again, unrealistic for VM's IO.

I suggest using fio and such. See https://github.com/pcuzner/fio-tools for example.

When testing on the gluster mount point using above command I hardly get 10MB/s. (On the same time the network traffic hardly reaches 100Mbit).

When testing our of the gluster (for example at /root) I get 600 - 700MB/s.

That's very fast - from 4 disks doing RAID5? Impressive (unless you use caching!). Are those HDDs or SSDs/NVMe?

When I mount the gluster volume with NFS and test on it I get 90 - 100 MB/s, (almost 10x from gluster results) which is the max I can get considering I have only 1 Gbit network for the storage.

Also, when using glusterfs the general VM performance is very poor and disk write benchmarks show that is it at least 4 times slower then when the VM is hosted on the same data store when NFS mounted.

I don't know why I hitting such a significant performance penalty, and every possible tweak that I was able to find out there did not make any difference on the performance.

The hardware I am using is pretty decent for the purposes intended:
3 nodes, each node having with 32 MB of RAM, 16 physical CPU cores, 2 TB of storage in RAID5 (4 disks), of which 1.5 TB are sliced for the data store of ovirt where VMs are stored.

You have not mentioned your NIC speeds. Please ensure all work well, with 10g.

Is the network dedicated for Gluster traffic? How are they connected?

The gluster configuration is the following:

Which version of Gluster are you using?

Volume Name: vms
Type: Replicate
Volume ID: 4513340d-7919-498b-bfe0-d836b5cea40b
Status: Started
Snapshot Count: 0
Number of Bricks: 1 x (2 + 1) = 3
Transport-type: tcp
Bricks:
Brick1: gluster0:/gluster/vms/brick
Brick2: gluster1:/gluster/vms/brick
Brick3: gluster2:/gluster/vms/brick (arbiter)
Options Reconfigured:
nfs.export-volumes: on
nfs.disable: off
performance.readdir-ahead: on
transport.address-family: inet
performance.quick-read: off
performance.read-ahead: off
performance.io-cache: off
performance.stat-prefetch: on

I think this should be off.

performance.low-prio-threads: 32
network.remote-dio: off

I think this should be enabled.

cluster.eager-lock: off
cluster.quorum-type: auto
cluster.server-quorum-type: server
cluster.data-self-heal-algorithm: full
cluster.locking-scheme: granular
cluster.shd-max-threads: 8
cluster.shd-wait-qlength: 10000
features.shard: on
user.cifs: off
storage.owner-uid: 36
storage.owner-gid: 36
network.ping-timeout: 30
performance.strict-o-direct: on
cluster.granular-entry-heal: enable
features.shard-block-size: 64MB

I'm not sure if this should not be 512MB. I don't remember the last resolution on this.

performance.client-io-threads: on
client.event-threads: 4
server.event-threads: 4
performance.write-behind-window-size: 4MB
performance.cache-size: 1GB

In case I can provide any other details let me know.

What is your tuned profile?

At the moment I already switched to gluster based NFS but I have a similar setup with 2 nodes where the data store is mounted through gluster (and again relatively good hardware) where I might check any tweaks or improvements on this setup.

Thanx

On Wed, Sep 6, 2017 at 5:32 PM, Yaniv Kaul <ykaul@redhat.com> wrote:

On Wed, Sep 6, 2017 at 3:32 PM, Abi Askushi <rightkicktech@gmail.com> wrote:
Hi All,

I've playing with ovirt self hosted engine setup and I even use it to production for several VM. The setup I have is 3 server with gluster storage in replica 2+1 (1 arbiter).
The data storage domain where VMs are stored is mounted with gluster through ovirt. The performance I get for the VMs is very low and I was thinking to switch and mount the same storage through NFS instead of glusterfs.

I don't see how it'll improve performance.
I suggest you share the gluster configuration (as well as the storage HW) so we can understand why the performance is low.
Y.

The only think I am hesitant is how can I ensure high availability of the storage when I loose one server? I was thinking to have at /etc/hosts sth like below:

10.100.100.1 nfsmount
10.100.100.2 nfsmount
10.100.100.3 nfsmount

then use nfsmount as the server name when adding this domain through ovirt GUI.
Are there any other more elegant solutions? What do you do for such cases?
Note: gluster has the back-vol-file option which provides a lean way to have redundancy on the mount point and I am using this when mounting with glusterfs.

Thanx

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