I strongly believe that FUSE mount is the real reason for poor performance in HCI and these minor gluster and other tweaks won't satisfy most seeking i/o performance. Enabling libgfapi is probably the best option. Redhat has recently closed bug reports related to libgfapi citing won't fix and one comment suggests that libgfapi was not showing good enough performance to bother with which appears to contradict what many oVirt users are seeing. It's confusing to me why libgfapi as a default option is not being given any priority. https://bugzilla.redhat.com/show_bug.cgi?id=1465810 "We do not plan to enable libgfapi for oVirt/RHV. We did not find enough performance improvement justification for it" On Tue, Mar 24, 2020 at 3:34 PM Alex McWhirter <alex@triadic.us> wrote:
Red hat also recommends a shard size of 512mb, it's actually the only shard size they support. Also check the chunk size on the LVM thin pools running the bricks, should be at least 2mb. Note that changing the shard size only applies to new VM disks after the change. Changing the chunk size requires making a new brick.
libgfapi brings a huge performance boost, in my opinion its almost a necessity unless you have a ton of extra disk speed / network throughput. Just be aware of the caveats.
On 2020-03-24 14:12, Strahil Nikolov wrote:
On March 24, 2020 7:33:16 PM GMT+02:00, Darrell Budic <budic@onholyground.com> wrote:
Christian,
Adding on to Stahil’s notes, make sure you’re using jumbo MTUs on servers and client host nodes. Making sure you’re using appropriate disk schedulers on hosts and VMs is important, worth double checking that it’s doing what you think it is. If you are only HCI, gluster’s choose-local on is a good thing, but try
cluster.choose-local: false cluster.read-hash-mode: 3
if you have separate servers or nodes with are not HCI to allow it spread reads over multiple nodes.
Test out these settings if you have lots of RAM and cores on your servers, they work well for me with 20 cores and 64GB ram on my servers with my load:
performance.io-thread-count: 64 performance.low-prio-threads: 32
these are worth testing for your workload.
If you’re running VMs with these, test out libglapi connections, it’s significantly better for IO latency than plain fuse mounts. If you can tolerate the issues, the biggest one at the moment being you can’t take snapshots of the VMs with it enabled as of March.
If you have tuned available, I use throughput-performance on my servers and guest-host on my vm nodes, throughput-performance on some HCI ones.
I’d test with out the fips-rchecksum setting, that may be creating extra work for your servers.
If you mounted individual bricks, check that you disabled barriers on them at mount if appropriate.
Hope it helps,
-Darrell
On Mar 24, 2020, at 6:23 AM, Strahil Nikolov <hunter86_bg@yahoo.com> wrote:
Hey Strahil,
seems you're the go-to-guy with pretty much all my issues. I thank you for this and your continued support. Much appreciated.
200mb/reads however seems like a broken config or malfunctioning gluster than requiring performance tweaks. I enabled profiling so I have real life data available. But seriously even without tweaks I would like (need) 4 times those numbers, 800mb write speed is okay'ish, given
fact that 10gbit backbone can be the limiting factor.
We are running BigCouch/CouchDB Applications that really really need IO. Not in throughput but in response times. 200mb/s is just way off.
It feels as gluster can/should do more, natively.
-Chris.
Hey Chris,,
You got some options. 1. To speedup the reads in HCI - you can use the option : cluster.choose-local: on 2. You can adjust the server and client event-threads 3. You can use NFS Ganesha (which connects to all servers via
On 24/03/2020 06:17, Strahil Nikolov wrote: libgfapi) as a NFS Server.
In such case you have to use some clustering like ctdb or
On March 24, 2020 11:20:10 AM GMT+02:00, Christian Reiss <email@christian-reiss.de> wrote: the pacemaker.
Note:disable cluster.choose-local if you use this one 4 You can try the built-in NFS , although it's deprecated (NFS Ganesha is fully supported) 5. Create a gluster profile during the tests. I have seen numerous improperly selected tests -> so test with real-world workload. Synthetic tests are not good.
Best Regards, Strahil Nikolov
Hey Chris,
What type is your VM ? Try with 'High Performance' one (there is a good RH documentation on that topic).
If the DB load was directly on gluster, you could use the settings in the '/var/lib/gluster/groups/db-workload' to optimize that, but I'm not sure if this will bring any performance on a VM.
1. Check the VM disk scheduler. Use 'noop/none' (depends on multiqueue is enabled) to allow the Hypervisor aggregate the I/O requests from multiple VMs. Next, set 'noop/none' disk scheduler on the hosts - these 2 are the optimal for SSDs and NVME disks (if I recall corectly you are using SSDs)
2. Disable cstates on the host and Guest (there are a lot of articles about that)
3. Enable MTU 9000 for Hypervisor (gluster node).
4. You can try setting/unsetting the tunables in the db-workload group and run benchmarks with real workload .
5. Some users reported that enabling TCP offload on the hosts gave huge improvement in performance of gluster - you can try that. Of course there are mixed feelings - as others report that disabling it brings performance. I guess it is workload specific.
6. You can try to tune the 'performance.readahead' on your gluster volume.
Here are some settings of some users /from an old e-mail/:
performance.read-ahead: on performance.stat-prefetch: on performance.flush-behind: on performance.client-io-threads: on performance.write-behind-window-size: 64MB (shard size)
For a 48 cores / host:
server.event-threads: 4 client.event-threads: 8
Your ecent-threads seem to be too high.And yes, documentation explains it , but without an example it becomes more confusing.
Best Regards, Strahil Nikolov
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When talking about mounts, you can avoid SELINUX lookups via 'context=system_u:object_r:glusterd_brick_t:s0' mount option for all bricks. This way the kernel will reduce the requests to the bricks.
Also 'noatime' is a default mount option(relatime is also a good one) for HCI gluster bricks.
It seems you have a lot of checks to do :)
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