The right switch for iSCSI

[Sly]

I am planning to purchase an iSCSI SAN (HP MSA2324i). Connections on the SAN and servers will be 1GbE. There are some good threads and articles that point out how important it is to configure the network infrastructure to optimize iSCSI throughput (i.e. jumbo packets, buffering, port aggregation, flow control, backbone throughput on the switch, etc.,). I am considering the following switches. Which ever one I purchase will be dedicated to the trafic between the iSCSI SAN and the ESX hosts, and 24 ports will be more than enough, so I do not need to worry about being able to stack additional switches onto these.

1) HP 2910AL-24G switch

2) Cisco Catalyst 3560G

Is there a better Cisco switch for iSCSI 1GbE copper? My company prefers Cisco switches, but when I contacted Cisco they advised the Cisco MDS 9216i switch. This seems like significant overkill to me. Please advise.

[Sly]

Gabriel,

I have to agree with you based on what I have read and been told over the last week. Since this is the backbone of the iSCSI infrastructure, don't skimp on the switches. I have narrowed it down to the HP 2910al. It is rated at 128Gbps and has the features I need and is priced much lower than most Cisco hardware. If that isn't paletable to my IT dept then I think I will go with the Cisco Catalyst 3750G series and make sure the IOS is up to date to support flow control properly.

Thanks to everyone for your help on this,

David.

[jayctd]

Sounds to me like they corrected the problem that we had with earlier models ... assuming their documentation is right (and it should be) you should have your most important basis covered.

We have used the procurve line for access and distribuation layer switches for quite some time with pretty good reliability so for an entry level you should be good

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[jayctd]

We run a mixed line of SATA and SAS depending on workload and profile.

To be honest we have had a few observations

1) SATA performs well with that many disks under it, I would note that we choose SMALLER disks (500 GB) to keep the disk to GB ratio low

2) We operated system drives on a SATA backbone with medium to good performance untill the 200 virtual mark (at which point we got poor performance on boot storms like patch tuesdays)

As such we now operate with SAS under system and a mix of SAS and SATA directly attached using MSISCSI dependidng on load, you may at your size be able to get buy without the expense.

Its something to test.

If needed i can give you some numbers for IOPS that we see but you may not have much to compare them to

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[jayctd]

We went that way but we needed the stacks

If you so choosethe 3750 has been a great line for our ISCSI (2 redundant stacks of 3, 48 port switches each right now)And we are no where neer pushing the limits of the stacks or the port channels between them

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[marktbreaux]

So in your experience running an MSA2313i with 12 500GB SATA drives in RAID 10 would be good for an 8-12 VM house? I am going to go with vSphere 4 Essentials Plus because it will give me 3 physical server licenses so that I can use two at my main site and 1 at the DR site.

[jayctd]

Yeah I think you would be fine, we got 30 or 40 Exchange/SQL/DC virtuals out of roughly the same hardware (actually RAID50 not 10 in our casE)

The sticking point is if you have a particularly heavy IOPS load servet, that configuration should load fine it is just if you have a large single profile machine that needs the pure IOPS.

Like any IT person I hate to speek in absolutes but what are the profile of the servers you are talking about?

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[marktbreaux]

I feel I maybe overtaking the point of this thread. If you want, can we talk on my discussion thread? HERE

[Virutal_Me]

I hope this question isn't too far off track: I am trying to better understand how to configure iscsi storage to to support a vm cluster. The Vm portion is understood but, I understand that iscsi uses names and shares IP address: am looking for some docs on how to configure a cisco switch to support a iscsi configuration. I have been looking through cisco related docs to no avial, any assistance in this would be apperciated

Thanks Dave

[EllettIT]

The 3750 seem's to be the del-facto standard for iSCSI switching as most folks do want the high speed stacking link between the switches. Certainly, it's a great switch however not the cheapest That said I'm using 2 of the HP 2910al's in our environment and everything seems to be going ok with it. I did speak to HP before the purchase and flow control and jumbo frames are supported at the same time on the switch. If you're purchasing more than one (which would be the best practice) then HP has a low cost stacking module for those switches (J9165A). Otherwise I'd look at an 4-8 port trunk between the switches. HP has some other options that are more expensive but are more "enterprise" class switches (bigger packet buffers etc). The one's that I looked at in addition to the 2910al's:

3500 http://www.procurve.com/products/switches/HP_ProCurve_Switch_3500yl_Series/overview.htm

6600 http://www.procurve.com/products/switches/HP_ProCurve_6600_Switch_Series/overview.htm

[EllettIT]

Dave,

some of the "best practices" in regards to iSCSI configuration on your switches:

- Hard code the ports to 1000 full duplex

- Enable jumbo frames (make sure your switch supports this)

- Enable flow control (make sure your switch supporst this, may not be able to enable both Jumbo and Flow Control at the same time, check spec's of switch)

- Disable Spanning Tree (one of the newer spanning tree standards may work in an iSCSI environment but I'd stay away from the classic version)

- Disable unicast storm control (ciso feature I think, don't see anything comparible on my HP switch)

I'm most definately NOT an expert on this so double check on these settings for your situation. As far as the specific's on the config I would think that should be easy enough to find out with the switch documentation.