Re: [CentOS] bad iscsi performance after upgrade to CentOS 7.2

[Steven Tardy]

> On Jun 20, 2016, at 5:15 AM, Ulrich Leodolter  
> wrote:
> 
> has anyone an idea why iSCSI read performance degraded in CentOS 7.2 ?

I'm not sure about those versions of centos, but iSCSI throughput being TCP is 
dependent on TCP receive window and packet loss. Tcpdump to see if the TCP 
window changed between those versions of centos.
___
CentOS mailing list
CentOS@centos.org
https://lists.centos.org/mailman/listinfo/centos

[CentOS] bad iscsi performance after upgrade to CentOS 7.2

[Ulrich Leodolter]

hi all,

after i upgraded a physical server (SUN FIRE X4170) from CentOS 6.8 to 7.2
i am not able to get the same iSCSI read performance.

the server is connected to HP P2000 Storage via 2 x 1GbE Ethernet.

CentOS 6.8 gives me full read performance on raw iSCSI devices /dev/sdxx at 
115MB/s.
CentOS 7.2 allows only 90-100MB/s, read performance varies and is not stable 
like for 6.8

the multipath performance on 7.2 is even worse.

CentOS 6.8 allows to read a full speed and stable 220MB/s.
CentOS 7.2 maximum was 140MB/s after i disabled readahead for multipath devices 
in tuned.

btw. i tried many recommended optimizations in 7.2, but i am not getting the 
raw iSCSI read
performance than on 6.8,  and on 6.8 i had no special tuning für iSCSI.

mtu 9000 is set and verified for both OS, other settings like network buffers 
are almost identical.

has anyone an idea why iSCSI read performance degraded in CentOS 7.2 ?

best regards
ulrich
___
CentOS mailing list
CentOS@centos.org
https://lists.centos.org/mailman/listinfo/centos