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Xenserver 5.5 connected to iscsi SAN

Posted on 2011-10-19
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I have dell poweredge r710 servers with (8) 1G eithernet ports.
I ran two cat6 cables for data to my LAN switches
I ran two cat6 cables to my iscsi switches.

my question is:
is it best to add a bound network for port x and y on the xenserver.
Then create a interface for that for the iscsi san.
or just give each port its own ip address and let god sort it out?

Same question for the LAN side.

I guess my thinking is if im doing that on the xenserver, do the switches need to know about it? Or does it just work?  Either way is there ea benefit to one big 2gig pipe vs 2 1 gig pipes?
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Question by:Eric
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by:
bhanukir7 earned 336 total points
ID: 37001379
hi ecszone,

one big 2gig pipe is always going to be better than 2 1 gig pipes if the purpose is of them is the same,

as long as the XENserver has the right modules to create that bond network and handle network issues you should not have any issues.

you can certainly try to validate this for few days and run some stress tests in a test bed environment to verify if you have any network latency when configured with bond interface.

regards
bhanu
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by:Eric
ID: 37001407
Citrix xenserver has the bond feature built in.  I just have been ahvinb performance issues.  I have no reason to belive its the SAN besides that I  dont know waht else to look at.

I though maybe because i created the bond on xenserver, but the hp procurve switch does not know its a trunk (what procurve calls bounded ports)
I never done a trunk on a procurve, i just read about it in the past.
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Assisted Solution

by:ddotson
ddotson earned 1332 total points
ID: 37003813
From what we see and what I've read, Xenserver bonds DO NOT double your bandwidth.  They are an active/passive failover kind of thing.  Because of that, you don't need to do anything on your switch.  In XenServer 6, when you setup a bond, you get to select "active/active" or "active/passive".  Not sure if that REALLY means that you get to "double" your bandwidth.  

Keep in mind that even if you bond them together, a single network conversation takes place via one nic - at 1 Gb.  Add conversations in to different devices, then you start seeing the benefits.
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by:ArneLovius
ArneLovius earned 332 total points
ID: 37015075
you need to look at MPIO not bonding, but your iSCSI controller needs to support it.
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Author Comment

by:Eric
ID: 37017444
Dell does not make a hitkit for xenserver version of linux. Its an equalogic san. So wo a hitkit no matter what I do I'm only sharing a single gig port across all vm's :(

Wish I went with vmware or hyper-v
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Assisted Solution

by:ddotson
ddotson earned 1332 total points
ID: 37017628
It still works...  If you need smoking performance, you probably shouldn't be virtualizing th workload anyway.
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by:Eric
ID: 37018420
One gig does not seem that much if your have 10+ VM's on it.
Although it never seems maxed out. We are getting high pagging levels.
So i was thinking maybe it was the pipe to the SAN slowing down paging.

 screenshot
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Expert Comment

by:ddotson
ID: 37018437
We are working on performance issues as well.  We are running 10Gb Equallogic with Xenserver 5.6.  We thought we'd get smoking performance out of 10Gb, but Dell is saying that only the largest workloads tax even the 1Gb stuff.  Really??
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by:Eric
ID: 37018695
heh.
what is your performance issue?
did you isolate it  at all?
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Assisted Solution

by:ddotson
ddotson earned 1332 total points
ID: 37018725
It's looking like the hypervisor, but I can't tell you where yet.  I have run rudimentary IO tests using IOmeter on both a physical machine running Windows 2008r2, and XenServer 5.6 and 6.0 virtual machines.  The physical machine can use MPIO and it gets smoking performance.  The virtual machines get OK performance.

I'm setting up a VMware ESXi host.  Initial tests from a VM there are dismal.  I'm sure it's a configuration issue.

I'd like the smoking performance, please.
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by:Eric
ID: 37018757
LOL same.
im going to try hyper-v as im told the hitkit is easy to get working.

I even have the recommended force10 iscsi switches.  it should be rocking.
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Expert Comment

by:ddotson
ID: 37018773
Interesting.  We bought Cisco switches and then with the issues we have been having, Dell recommended the Force10.  They offered a demo, but we are getting things ironed out with the Cisco, so we declined.

I can tell you that all of the Equallogic engineers have nothing good to say about Hyper-V.  That was at the Equallogic conference a year ago in San Diego, though.  Someone else said that Hyper-V has gotten much better.
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by:Eric
ID: 37018821
hmm.  I was kind of against it.  But our exchange consultants recommended it. at the same time i realized a hitkit does not exist for xenserver.

Here are some of my SAN HQ graphs for some of the days we had performance issues.  seems ok i think... sanHQ screen
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Expert Comment

by:ddotson
ID: 37018853
We are seeing high retransmits to the XenServer hosts.  You can see the retransmits in the GUI, but you can't tell much more.  We have an open case with Dell and they just informed me this AM that it's between the SAN and the hosts!  We thought it was due to replication over a slow(er) link.

Have you checked that?
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by:Eric
ID: 37018915
Where do you see that?
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Expert Comment

by:ddotson
ID: 37019100
Click on "Network" in SANHQ.
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by:Eric
ID: 37019386
Sorry i thought you meant you found something through the xencenter gui.

 sanhq_net
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Expert Comment

by:ddotson
ID: 37019398
Retransmits looks great...
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by:Eric
ID: 37019403
I cant imagine that percent is significant.    i would guess its less than 1%
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Expert Comment

by:ddotson
ID: 37019412
Dell wants to see it under 1%.
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Author Comment

by:Eric
ID: 37040131
so back to the original question.  AM i stuck to 1Gb/s for an entire xenserver host?
seems like bonding just adds redundency
and xenserver does not have a "hitkit" for MPIO

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by:Eric
ID: 37040144
semi-unrelated, i created a new ticket specifically trying to figure out why my citrix VMS are slow.

http://www.experts-exchange.com/Software/Virtualization/Q_27418555.html

I am tempted to build a new physical machine and scrap virtualizing my terminal servers.
Of coarse i have no idea thats the issue.

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Expert Comment

by:ArneLovius
ID: 37041046
I don't know what a "hitkit" is, but MPIO on Xenserver is certainly possible, granted this is quite old but... http://cns-service.blogspot.com/2008/02/xenserver-mpio.html

Your other option of course is to just have boot volumes go through the host and have data volumes in the guests connect directly to your iSCSI SAN for other volumes, this would enable you to allocate multiple NICs for iSCSI operations.

you shouldn;t be seeing _any_ restransmits, unless you've got a bottleneck, how many spindles in your SAN ?

depending on the workloads in your hosts, I'd be tempted to use most of your NICs for iSCSI rather than server - client connectivity, unless you've got people opening _huge_ files in the TS environment, storage bandwidth to the SAN (and IOPS on the SAN) is going to be much more important.



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by:Eric
ID: 37041771
All the counters on the SAN are "ideal" according to my dell engineer.  At least the Iops/latency and Que length.

Its something deeper Im guessing .. something in connectivity to the SAN , a configuration thing, possibly with the VM's. or maybe even the guest os.

i just wish there was a simple performance monitor that would tell me whats the bottleneck.  im losing my mind.  

as far as that article, im real scared to do that as im not a linux guy.  IF that is a few versions of xenserver old, who knows what I might break.

Maybe ill call Dell and see wht they got for me.  From my expeirence nobody knows anything about xenserver.  The dell xenserver support staff always say "sorry i am a VMware guy"

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Expert Comment

by:ddotson
ID: 37042051
That's the first article I've seen talking about MPIO and Xenserver.  Even Citrix will tell you it's not supported.  So possible: yes.  Supported: No.  I wouldn't stake productions VMs on that.

The hitkit being referenced is the Dell Equallogic Host Integration Toolkit.

The one thing that we haven't talked about is your user environment.  What will you be virtualizing and for whom?
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by:Eric
ID: 37042108
Mainly we are virtualizing our xenapp farm. I'd like to consider exchange someday and some light load sql servers. Ill keep my sql server on a standalone
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Expert Comment

by:ddotson
ID: 37042137
We've got everything virtualized.  XenApp, SQL, Exchange, etc.  We are working through the performance issues, and I think it's going to get better.  There is anecdotal information out in our group that we are seeing better performance in XenApp than we did with VMware.  But, that was a long time ago.

I am preparing to move a VM SQL box back to physical and store the data on the SAN.  Microsoft's licensing is too crazy not to do that.
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Expert Comment

by:bhanukir7
ID: 37042174
there is certainly a citrix document that talks about multipathing iSCSI on XENserver

http://support.citrix.com/article/CTX129309


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by:Eric
ID: 37045916
hmm thats for 5.6  5.6 no longer supports embeded xenserver. i would need to change to citrix licensing and install hard drives for the host. so for the near future ill be staying on 5.5 unfortunatly.
Ill see if i can find the same doc for 5.5
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Expert Comment

by:ddotson
ID: 37059633
You can't multipath to Equallogic SANs.
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by:Eric
ID: 37063045
ever? or you mean specifically in xenerver 5.5?

because my engineer told me for sure i can with hyper-v
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Assisted Solution

by:ddotson
ddotson earned 1332 total points
ID: 37064592
With XenServer.  I am multipathing with Windows 2008r2 on bare metal.  My tests show that I'm getting pretty darn good performance.
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by:Eric
ID: 37139992
oh so you just cant multipath to a equalogic san?

thought you had equalogic  also.
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Expert Comment

by:ddotson
ID: 37140274
You can't natively in XenServer.  I think you can in Vmware.  Not sure about HyperV.

To this point, we have bonded 2 10GB nics and have used that for storage traffic.  I'm going to try breaking the bond, passing the two nics through to the guest, and then use the HIT kit to multipath.  See what that does for us....
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Expert Comment

by:ddotson
ID: 37140278
We are an equallogic shop, btw.
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Author Comment

by:Eric
ID: 37141339
Oh, i think you confsued me when you said:
ddotson:
You can't multipath to Equallogic SANs.

I thought about going that route, but it adds alot of steps. plus the native boot volume is still using the bound way (which is also how im setup)
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Expert Comment

by:ddotson
ID: 37141733
Yeah - seems kludgy.  I've got to try it to see if the performance is better, though.  :)
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by:Eric
ID: 37171099
waiting to see ddotson's results.  DO not close.
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by:Eric
ID: 37221880
.
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Expert Comment

by:ddotson
ID: 37229542
Holy cow...

So we got VMware setup and ran the same IOmeter tests that we have run in every conceivable combination on XenServer.

We are seeing 8-9 times better performance in Vmare than we are in Xenserver.  In fact, the CIO said that we will be moving back to Vmware.
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by:Eric
ID: 37237999
hmm.  interesting.  My dell rep said they had some large scale implementations moving from vmware to xen for performance reasons.

I wish i went vmware.  im too deep to change now. i dont have the manpower.
:(
thanks for the info
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Expert Comment

by:ddotson
ID: 37238068
Dell said that?  In all of my conversations, Xen is hardly a whisper on Dell's lips.  All of the Equallogic engineers at the Equallogic conference gave us blank stares when we told them we were using Xen.  :)

VMware is infinitely more complicated.  We were using 3.x I think before we switched over.  It didn't handle the storage as nicely as Xen.  I'm not looking forward to moving back.
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Author Comment

by:Eric
ID: 37238818
Interesting. I only used the free version of it.  So i don't know how complicated it is i guess.

They said a few big customers did because they tuned xen for significantly improved performance.  i don't remember who.  But they were huge companies. Maybe its application specific.   I think they were trying to comfort me because i said I wish I went with vmware.
And it worked, knowing im not the only one using XEN.

When i decided an article mentioned citrix was heavily devoted, they would be the first to have supported SQL and Exchange support from Microsoft for Virtualizaiton.  Blah blah

I don't know if that every came true as im not putting my servers in a VM because i don't have the confidence yet.

The article also mentioned xenserver is 10-20% more efficant with xen app which is the core of our infrastructure.
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Expert Comment

by:ddotson
ID: 37239416
Our guys saw a performance increase in XenApp.

I'm not down on XenServer - they do a lot of things I wish VMware did.  Storage is easier, VM management is easier, etc.  But passing all network traffic through Dom0 seems to be a problem for ISCSI traffic.
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Author Comment

by:Eric
ID: 37239507
Dom0?
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Expert Comment

by:ddotson
ID: 37240418
That's the XenServer OS...
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Author Comment

by:Eric
ID: 37240483
lol. i never heard that before.
I heard xenserver and knew it was linux.  to funny.
your talking about citrix xenserver right? not the open source version?
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Expert Comment

by:ddotson
ID: 37240964
Correct.
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Expert Comment

by:ddotson
ID: 37240966
Vmware is a linux variant too.  
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Expert Comment

by:ddotson
ID: 37265454
Thanks for including me on the solution.   My first time!

Enjoyed talking with you.
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by:Eric
ID: 37273384
Yea i dont know i had a clearn "answer:" but all the info was helpful. Its nice when someone is willing to discuss issues vs quick links to other sites just trying to get the points.
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