[Openstack] Download file from swift extremely slow

dongjh at ahope.com.cn dongjh at ahope.com.cn
Thu Jan 5 02:56:33 UTC 2017

In the [filter:cache] section, configure the memcached location:
use = egg:swift#memcache
memcache_servers = controller:11211

memcache_server or memcached_server ?

董 建 华
Email:dongjh at ahope.com.cn
From: Nasir Mahmood
Date: 2017-01-05 02:25
To: Rick Jones
CC: openstack
Subject: Re: [Openstack] Download file from swift extremely slow
Just a side note, can you please run the 'iostat -xnpz 1' on your swift nodes  and share results while downloading file , including network performance tests suggested earlier ... 

I would also suggest to share the logs on swift nodes would be much helpful on this by enabling debug in config.

On Jan 4, 2017 22:51, "Rick Jones" <rick.jones2 at hpe.com> wrote:
On 01/04/2017 12:59 AM, dongjh at ahope.com.cn wrote:
Hi experts

I finished the swift installation following the install
file upload  is very fast, but file download is extremely slow, why ?

[root at controller admin]#* time openstack object create container1 cirros-0.3.4-x86_64-disk.img*
| object                       | container  | etag                             |
| cirros-0.3.4-x86_64-disk.img | container1 | ee1eca47dc88f4879d8a229cc70a07c6 |

real    0m3.807s
user    0m2.127s
sys     0m0.161s

[root at controller /]#* time  openstack object save container1 cirros-0.3.4-x86_64-disk.img*
real    5m51.489s
user    5m48.172s
sys     0m2.094s

Are you able to run something like netperf or iperf between your client and the swift proxy?  For example:

netperf -H <proxy>    # get a feel for "to swift" basic network perf
netperf -H <proxy> -t TCP_MAERTS # get a feel for "from swift"

The idea there is to measure the network separate from the storage and swift processing, and go from there.

If there isn't much else happening on your setup at the time, you could also look at some snapshots of netstat -s on the proxy when you are downloading the object - look to see if there are many TCP retransmissions.  You can get something similar "directly" for the netperf tests with:

netperf -H <proxy> -- -o throughput,local_transport_retrans,remote_transport_retrans

netperf -H <proxy> -t TCP_MAERTS -- -o throughput,local_transport_retrans,remote_transport_retrans

rick jones

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