DSS V7 bad Performance

[bwb]

Hello

I'm running all my servers on a SAN DSS V6 (Dell PE2950 + Dell MD1000). Performance are good.

Now i have to setup a new SAN with DSS V7.
This V7 SAN is installed on exactly/identical configuration as the V6 SAN.

Config
Dell PE 2950 + Dell MD1000 + 4 x SAS 15k 300GB Raid 10 (Read ahead + Write back) on Perc 6 (this is the test datastore)
DSS V7 + 2 GB NIC for MPIO
ESX 5.1 + 2 GB NIC for MPIO + policy RoundRobin 1 iops
no jumbo frame
target SCST, block/io


the V7 SAN is running with twice less performance than the V6 SAN.

what i have to check now ?


Thanks

[Al-S]

What is the build of V7 that you are running? Also what are your NIC cards brand/model ?

[bwb]

I am running the latest build of openE (v.7.00 up05 6806).
NIC are integrated broadcom 5708/5709.

i notice that the 50% performance are only on volume where "replication mode" is ticked (i am preparing active/active DSSV7 SAN).
on DSS7 volume without this setting, the performance seems correct.

[Al-S]

If you are preparing the system, and applied the Replication to your system, for sure first time the replication running it would take some resources and bandwidth, but after finishing the replication ( for first time ) you will not notice that. Mostly that's why with your old system ( with V6 ) you did not notice it, because it is already done before time. So please wait tell the replication is done between your systems, then you can compare the performance again.

For your NIC cards, are they supporting the second generation of NetXtreme ? or only the first one? as we already have a small update file for the NetXtreme that support second generation, which should give you a more better performance too, to get this small update, please open a support ticket and our support team will support you with it.

[bwb]

I did not activate the replication feature.
I've just ticked the replication parameter on the volume group. i run only 1 V7 DSS for the moment.
Ticket is opened to get this update.

[Alex-Joda]

If you check the replication feature on the volume group it cost you nearly 2/3 of the performance compared to a VG without this checked. This is especially the case for IOPS. This happens regardless of running a replication task or not. We tested that very intense with some SSDs in a RAID 0 configuration, where you can see some nice IOPS numbers without replication and a hefty penalty after activating it. This is a sad thing because the active-active feature relies on the replication and this is the most important new feature of DSS7. Hopefully this will improve with newer versions....

[Al-S]

When using some specific settings, with V7, the performance compared with V6 is dropped down. And we are working on this issue and we will fix it very soon.
As mentioned, not all users with V7 or A/A (active - active) will face this issue. And in urgent cases, you can use V6 at the moment tell we update this issue and fix it.

[JMC-Software]

Do you enabled Caching on the RAID controller?

We have the same performence issue with replication and failover.

IOMETER: (OpenPerformenceTest - Max Throughput 100% Read )
500 GB LUN, Block, Test on a Hyper-V Server

IOPS, MBPS, Response Time
Only one SAN, 17368.182502,542.755703,3.263848
with Replication: 15586.519347,487.07873,3.664976
with Failover: 15373.858457,480.433077,3.790156

[bwb]

i am using adaptative read ahead and write back on the controllers.
my problem is not solved at this time.

[Gr-R]

to optimize the raid:
-write policy: write-back caching
-read policy: read ahead
-Cache Policy: Cached
-Disk cache policy: Enabled