[Gluster-users] performance.cache-size for high-RAM clients/servers, other tweaks for performance, and improvements to Gluster docs

Artem Russakovskii archon810 at gmail.com
Fri Apr 6 08:12:11 UTC 2018

Hi again,

I'd like to expand on the performance issues and plead for help. Here's one
case which shows these odd hiccups: https://i.imgur.com/CXBPjTK.gifv.

In this GIF where I switch back and forth between copy operations on 2
servers, I'm copying a 10GB dir full of .apk and image files.

On server "hive" I'm copying straight from the main disk to an attached
volume block (xfs). As you can see, the transfers are relatively speedy and
don't hiccup.
On server "citadel" I'm copying the same set of data to a 4-replicate
gluster which uses block storage as a brick. As you can see, performance is
much worse, and there are frequent pauses for many seconds where nothing
seems to be happening - just freezes.

All 4 servers have the same specs, and all of them have performance issues
with gluster and no such issues when raw xfs block storage is used.

hive has long finished copying the data, while citadel is barely chugging
along and is expected to take probably half an hour to an hour. I have over
1TB of data to migrate, at which point if we went live, I'm not even sure
gluster would be able to keep up instead of bringing the machines and
services down.

Here's the cluster config, though it didn't seem to make any difference
performance-wise before I applied the customizations vs after.

Volume Name: apkmirror_data1
Type: Replicate
Volume ID: 11ecee7e-d4f8-497a-9994-ceb144d6841e
Status: Started
Snapshot Count: 0
Number of Bricks: 1 x 4 = 4
Transport-type: tcp
Brick1: nexus2:/mnt/nexus2_block1/apkmirror_data1
Brick2: forge:/mnt/forge_block1/apkmirror_data1
Brick3: hive:/mnt/hive_block1/apkmirror_data1
Brick4: citadel:/mnt/citadel_block1/apkmirror_data1
Options Reconfigured:
cluster.quorum-count: 1
cluster.quorum-type: fixed
network.ping-timeout: 5
network.remote-dio: enable
performance.rda-cache-limit: 256MB
performance.readdir-ahead: on
performance.parallel-readdir: on
network.inode-lru-limit: 500000
performance.md-cache-timeout: 600
performance.cache-invalidation: on
performance.stat-prefetch: on
features.cache-invalidation-timeout: 600
features.cache-invalidation: on
cluster.readdir-optimize: on
performance.io-thread-count: 32
server.event-threads: 4
client.event-threads: 4
performance.read-ahead: off
cluster.lookup-optimize: on
performance.cache-size: 1GB
cluster.self-heal-daemon: enable
transport.address-family: inet
nfs.disable: on
performance.client-io-threads: on

The mounts are done as follows in /etc/fstab:
/dev/disk/by-id/scsi-0Linode_Volume_citadel_block1 /mnt/citadel_block1 xfs
defaults 0 2
localhost:/apkmirror_data1 /mnt/apkmirror_data1 glusterfs defaults,_netdev
0 0

I'm really not sure if direct-io-mode mount tweaks would do anything here,
what the value should be set to, and what it is by default.

The OS is OpenSUSE 42.3, 64-bit. 80GB of RAM, 20 CPUs, hosted by Linode.

I'd really appreciate any help in the matter.

Thank you.


Founder, Android Police <http://www.androidpolice.com>, APK Mirror
<http://www.apkmirror.com/>, Illogical Robot LLC
beerpla.net | +ArtemRussakovskii
<https://plus.google.com/+ArtemRussakovskii> | @ArtemR

On Thu, Apr 5, 2018 at 11:13 PM, Artem Russakovskii <archon810 at gmail.com>

> Hi,
> I'm trying to squeeze performance out of gluster on 4 80GB RAM 20-CPU
> machines where Gluster runs on attached block storage (Linode) in (4
> replicate bricks), and so far everything I tried results in sub-optimal
> performance.
> There are many files - mostly images, several million - and many
> operations take minutes, copying multiple files (even if they're small)
> suddenly freezes up for seconds at a time, then continues, iostat
> frequently shows large r_await and w_awaits with 100% utilization for the
> attached block device, etc.
> But anyway, there are many guides out there for small-file performance
> improvements, but more explanation is needed, and I think more tweaks
> should be possible.
> My question today is about performance.cache-size. Is this a size of cache
> in RAM? If so, how do I view the current cache size to see if it gets full
> and I should increase its size? Is it advisable to bump it up if I have
> many tens of gigs of RAM free?
> More generally, in the last 2 months since I first started working with
> gluster and set a production system live, I've been feeling frustrated
> because Gluster has a lot of poorly-documented and confusing options. I
> really wish documentation could be improved with examples and better
> explanations.
> Specifically, it'd be absolutely amazing if the docs offered a strategy
> for setting each value and ways of determining more optimal values. For
> example, for performance.cache-size, if it said something like "run command
> abc to see your current cache size, and if it's hurting, up it, but be
> aware that it's limited by RAM," it'd be already a huge improvement to the
> docs. And so on with other options.
> The gluster team is quite helpful on this mailing list, but in a reactive
> rather than proactive way. Perhaps it's tunnel vision once you've worked on
> a project for so long where less technical explanations and even proper
> documentation of options takes a back seat, but I encourage you to be more
> proactive about helping us understand and optimize Gluster.
> Thank you.
> Sincerely,
> Artem
> --
> Founder, Android Police <http://www.androidpolice.com>, APK Mirror
> <http://www.apkmirror.com/>, Illogical Robot LLC
> beerpla.net | +ArtemRussakovskii
> <https://plus.google.com/+ArtemRussakovskii> | @ArtemR
> <http://twitter.com/ArtemR>
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