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Multipathing iSCSI low performace


Jiri Skryja

Question

Hello, I am using 2x Lenovo SR630 with Lenovo Storage V3700 V2. I would like to enable HA but before that I ma testing speed performace and moving VHD from XEN to SAN takes too long. I got it connected like that (pic. san-switch). So for one server theory speed should be aroung 4 Gbps but the actuall speed when I transfer VHD is between 40 - 60 MBps and not 400 MBps. Jumbo Frames are enabled end-to-end. XenServer shows 1000 Mbit/s per port, SAN has 1 Gbit/s iSCSI ports, switches shows 1000 Mbit/s too. Discs are SAS 15k and 10k. So I dont know why is it so slow, can you help me please? 

san-switch.png

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15 hours ago, Alan Lantz said:

Multipathing with bonding? Bad idea and not supported. Multipathing with iSCSI on single nics 

is the way to go or boding when you do NFS.  Basically on storage you need to go from 1Gb to

10Gb to see speed benefits instead of bonding.

 

--Alan--

 

Ou, so you mean that it should be direct connection between xen servers and my san? without switches?

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Okay, I tried to connect it directly from SAN to XEN servers and it is not working and I am getting little bit frustrated. I got ports like that (on picture empty-ports) how should I connect them to get it working please? And what about IP addresses etc? 

 

It tried config as on picture direct-connection and it is not working, iSCSI can't be connected.

empty-ports.png

direct-connection.png

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On 8/2/2021 at 2:12 AM, Alan Lantz said:

Right with iSCSI and two switches going to two storage controllers iSCSI should have

4 iscsi paths to access your LUNs. 

 

--Alan--

 

Yes, it should be 4 paths, now it shows 8 paths per server which is bad. So how it should be? I used 2 NICs from XEN because I wanted better performace. Can you draw it for me please? 

 

image.thumb.png.990c8744b0942c7a126a04859a1c98c1.png

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One port per host going to each switch. Bonding ports will not give you more bandwidth or more redundancy,

it will only lead to issues . You need to choose either bonding or multipathing, but not a combination of both.

multipathing is redundancy. If one switch goes down or a SAN controller goes down, the other path will be

used. When a host talks to a controller, you will do so unicast from a single nic on the host to a single nic on

a SAN controller. Multiple links will not increase your performance. 

 

--Alan--

 

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10 minutes ago, Alan Lantz said:

One port per host going to each switch. Bonding ports will not give you more bandwidth or more redundancy,

it will only lead to issues . You need to choose either bonding or multipathing, but not a combination of both.

multipathing is redundancy. If one switch goes down or a SAN controller goes down, the other path will be

used. When a host talks to a controller, you will do so unicast from a single nic on the host to a single nic on

a SAN controller. Multiple links will not increase your performance. 

 

--Alan--

 

Thank you. Ok so, if I get it right, it should be like that:

image.thumb.png.595c330d4b7ec4e886f348cb8b9376e9.png

And yellow lines can be first network (for example 192.168.100.0/24) and red lines will be second network (for example 192.168.101.0/24). Am I right? 

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15 hours ago, Tobias Kreidl said:

You want a configuration like this: https://subscription.packtpub.com/book/virtualization_and_cloud/9781849686167/3/ch03lvl1sec28/storage-multipathing

This should give you four paths to each host.

Note added: Don't forget that you need to enable multipathing on each host, and to do so, the host must first be put into maintenance mode.

 

-=Tobias

So it looks same as I send last time. Thank you man.

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Something else you need which I don't think has been discussed is likely a custom multipath.conf 

from Lenovo for your XenServers. I think I found mine online, sometimes you can find references

to where others have used them for RedHat.  The generic one with XenServer may work, but having

one from the vendor is much preferred.

 

--Alan--

 

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3 hours ago, Alan Lantz said:

Something else you need which I don't think has been discussed is likely a custom multipath.conf 

from Lenovo for your XenServers. I think I found mine online, sometimes you can find references

to where others have used them for RedHat.  The generic one with XenServer may work, but having

one from the vendor is much preferred.

 

--Alan--

 

Okay, so conenction should be fine now but I should change multipath.conf file for Lenovo file. It looks like that I should use default. 

image.thumb.png.af81c304eecbc435648d4859f78625e2.png

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