[Gluster-users] slow write perf for disperse volume
Xavier Hernandez
xhernandez at datalab.es
Tue Apr 25 07:03:17 UTC 2017
Hi Ingard,
On 24/04/17 14:43, Ingard Mevåg wrote:
> I've done some more testing with tc and introduced latency on one of my
> testservers. With 9ms latency artificially introduced using tc ( sudo tc
> qdisc add dev bond0 root netem delay 9ms ) to a testserver in the same
> DC as the disperse volume servers I get more or less the same throughput
> as I do when testing DC1 <-> DC2 (which has ~9ms ping).
>
> I know distribute volumes were more sensitive to latency in the past. At
> least I can max out a 1gig link with 9-10ms latency when using
> distribute. Disperse seems to max at 12-14MB/s with 8-10ms latency.
A pure distributed volume is a simple configuration that simply forwards
a request to one of the bricks. No additional overhead is needed.
However a dispersed 4+2 volume needs to talk simultaneously to 6 bricks,
meaning 6 network round-trips for every request. Additionally it needs
to keep integrity so one or more additional requests are needed.
If network latency is high, all these requests contribute to increase
the overall request latency, limiting the throughput.
Have you tried a replica 2 or 3 ? it uses very similar integrity
mechanisms so it'll also add some latency. Maybe not so much as a
dispersed 4+2, but it should be perceptible.
Another test to confirm that the limitation is caused by latency is to
do multiple writes in parallel. Each write will be limited by the
latency, but the aggregated throughput should saturate the bandwidth,
specially on a 1Gb ethernet.
Even better performance can be achieved if you distribute the writes to
multiple clients or mount points (assuming they are not writing to the
same file).
Xavi
>
> ingard
>
> 2017-04-24 14:03 GMT+02:00 Ingard Mevåg <ingard at jotta.no
> <mailto:ingard at jotta.no>>:
>
> I can confirm mounting the disperse volume locally on one of the
> three servers i got 211 MB/s with dd if=/dev/zero of=./local.dd.test
> bs=1M count=10000.
>
> Its not very good concidering 10gig network, but at least 20x better
> than 10-12MB/s
>
> 2017-04-24 13:53 GMT+02:00 Pranith Kumar Karampuri
> <pkarampu at redhat.com <mailto:pkarampu at redhat.com>>:
>
> +Ashish
>
> Ashish,
> Could you help Ingard? Do let me know what you find.
>
> On Mon, Apr 24, 2017 at 4:50 PM, Ingard Mevåg <ingard at jotta.no
> <mailto:ingard at jotta.no>> wrote:
>
> Hi. I can't see a fuse thread at all. Please see attached
> screenshot of top process with threads. Keep in mind this is
> from inside the container.
>
> 2017-04-24 12:17 GMT+02:00 Pranith Kumar Karampuri
> <pkarampu at redhat.com <mailto:pkarampu at redhat.com>>:
>
> We were able to saturate hardware with EC as well. Could
> you check 'top' in threaded mode to see if fuse thread
> is saturated when you run dd?
>
> On Mon, Apr 24, 2017 at 3:27 PM, Ingard Mevåg
> <ingard at jotta.no <mailto:ingard at jotta.no>> wrote:
>
> Hi
> I've been playing with disperse volumes the past
> week, and so far i can not get more than 12MB/s when
> i do a write test. I've tried a distributed volume
> on the same bricks and gotten close to gigabit
> speeds. iperf confirms gigabit speeds to all three
> servers in the storage pool.
>
> The three storage servers have 10gig nics (connected
> to the same switch). The client is for a now a
> docker container in a 2nd DC (latency roughly 8-9 ms).
>
> dpkg -l|grep -i gluster
> ii glusterfs-client
> 3.10.1-ubuntu1~xenial1 amd64
> clustered file-system (client package)
> ii glusterfs-common
> 3.10.1-ubuntu1~xenial1 amd64
> GlusterFS common libraries and translator modules
> ii glusterfs-server
> 3.10.1-ubuntu1~xenial1 amd64
> clustered file-system (server package)
>
> $ gluster volume info
>
> Volume Name: DFS-ARCHIVE-001
> Type: Disperse
> Volume ID: 1497bc85-cb47-4123-8f91-a07f55c11dcc
> Status: Started
> Snapshot Count: 0
> Number of Bricks: 1 x (4 + 2) = 6
> Transport-type: tcp
> Bricks:
> Brick1: dna-001:/mnt/data01/brick
> Brick2: dna-001:/mnt/data02/brick
> Brick3: dna-002:/mnt/data01/brick
> Brick4: dna-002:/mnt/data02/brick
> Brick5: dna-003:/mnt/data01/brick
> Brick6: dna-003:/mnt/data02/brick
> Options Reconfigured:
> transport.address-family: inet
> nfs.disable: on
>
> Anyone know the reason for the slow speeds on
> disperse vs distribute?
>
> kind regards
> ingard
>
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>
> --
> Pranith
>
>
>
>
> --
> Ingard Mevåg
> Driftssjef
> Jottacloud
>
> Mobil: +47 450 22 834 <tel:+47%20450%2022%20834>
> E-post: ingard at jottacloud.com <mailto:ingard at jottacloud.com>
> Webside: www.jottacloud.com <http://www.jottacloud.com>
>
>
>
>
> --
> Pranith
>
>
>
>
> --
> Ingard Mevåg
> Driftssjef
> Jottacloud
>
> Mobil: +47 450 22 834 <tel:+47%20450%2022%20834>
> E-post: ingard at jottacloud.com <mailto:ingard at jottacloud.com>
> Webside: www.jottacloud.com <http://www.jottacloud.com>
>
>
>
>
> --
> Ingard Mevåg
> Driftssjef
> Jottacloud
>
> Mobil: +47 450 22 834
> E-post: ingard at jottacloud.com <mailto:ingard at jottacloud.com>
> Webside: www.jottacloud.com <http://www.jottacloud.com>
>
>
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