[Gluster-users] Expected performance for WORM scenario

Ondrej Valousek
Mon, 12 Mar 2018 12:53:39 -0000

Hi,
Gluster will never perform well for small files.
I believe there is  nothing you can do with this.
Ondrej

From: gluster-users-bounces at gluster.org [mailto:gluster-users-bounces at
gluster.org] On Behalf Of Andreas Ericsson
Sent: Monday, March 12, 2018 1:47 PM
To: Gluster-users at gluster.org
Subject: [Gluster-users] Expected performance for WORM scenario

Heya fellas.

I've been struggling quite a lot to get glusterfs to perform even
halfdecently with a write-intensive workload. Testnumbers are from gluster
3.10.7.

We store a bunch of small files in a doubly-tiered sha1 hash fanout directory
structure. The directories themselves aren't overly full. Most of the data
we write to gluster is "write once, read probably never", so 99% of
all operations are of the write variety.

The network between servers is sound. 10gb network cards run over a 10gb (doh)
switch. iperf reports 9.86Gbit/sec. ping reports a latency of 0.1 - 0.2 ms.
There is no firewall, no packet inspection and no nothing between the servers,
and the 10gb switch is the only path between the two machines, so traffic
isn't going over some 2mbit wifi by accident.

Our main storage has always been really slow (write speed of roughly 1.5MiB/s),
but I had long attributed that to the extremely slow disks we use to back it, so
now that we're expanding I set up a new gluster cluster with state of the
art NVMe SSD drives to boost performance. However, performance only hopped up to
around 2.1MiB/s. Perplexed, I tried it first with a 3-node cluster using 2GB
ramdrives, which got me up to 2.4MiB/s. My last resort was to use a single node
running on ramdisk, just to 100% exclude any network shenanigans, but the write
performance stayed at an absolutely abysmal 3MiB/s.

Writing straight to (the same) ramdisk gives me "normal" ramdisk speed
(I don't actually remember the numbers, but my test that took 2 minutes with
gluster completed before I had time to blink). Writing straight to the backing
SSD drives gives me a throughput of 96MiB/sec.

The test itself writes 8494 files that I simply took randomly from our
production environment, comprising a total of 63.4MiB (so average file size is
just under 8k. Most are actually close to 4k though, with the occasional 2-or-so
MB file in there.

I have googled and read a *lot* of performance-tuning guides, but the 3MiB/sec
on single-node ramdisk seems to be far beyond the crippling one can cause by
misconfiguration of a single system.

With this in mind; What sort of write performance can one reasonably hope to get
with gluster? Assume a 3-node cluster running on top of (small) ramdisks on a
fast and stable network. Is it just a bad fit for our workload?

/Andreas

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