Why use a Software iscsi with initiator with a mezzanine card?

[wgaybba]

We have a consultant that is recommending to us that we should configure our iSCSI connections using the software initiator for the Dell BMC57711 mezzanine card. We don't understand why he would be recommending this configuration. We thought that iSCSI only has two chooses, hardware or software, but not both. He states in the documentation, that this is a way to use the software initiator to manage the iSCSI config, and the mezzanine card will still be able to handle to hardware acceleration. We are unable to verify his information for this recommendation. Could someone provide any further incite to this?

Thanks

Wayne

[a_p_]

I'm not familiar with Dell blades, so you may need to verify this in the documentation or maybe wait for another user who knows Dell's recommendations.

Anyway you basically have 3 options.

• Software iSCSI
• Hardware iSCSI (dependent)
• Hardware iSCSI (independent)

See e.g. SCSI Storage Overview for details.

André

[sparrowangelste]

it may be because "HW ISCSI HBA you are limited to the number of iSCSI targets you can connect to, 64"

http://en.community.dell.com/techcenter/storage/f/4466/t/19415128.aspx

you might not have that many luns then again you might have more

also according to http://www.vmadmin.co.uk/vmware/35-esxserver/252-esxihwswiscsijumbo

"jumbo frames cannot be used with this boradcom hardware dependant initiator."

so looks like software is the way to go

[wgaybba]

I see that Intel has a similar best practice.

http://www.dell.com/downloads/global/products/pedge/en/Optimizing-QoS-for-VMware.pdf

They state that you can achieve a high throughput if you use a software initiator. If you use a hardware initiator, you will loss the following features from VMware.

• No IPv6

• No DHCP

• No Routing

• No Network I/O Control

• No Traffic Shaping

• No iSCSI traffic reporting

• Security Vulnerabilities

I did not realize that iSCSI is really not that well designed. It really shows that it is a technical workaround to reduce cost.

Ok, so let’s say that we are going to use iSCSI. Which one will provide a better compromise, the VMware software initiator a software initiator in the Windows guest?

[sparrowangelste]

vmware software initiator is preffered over windows.

windows iscis is usually not recommended

[vmroyale]

Also know that in-guest initiators can also complicate your backup strategy.

[wgaybba]

This is now making a lot more sense, thanks to everyone for their input.

The consultant is stating that his config will also make use of multi-pathing. I have investigated this and it seems that VMware implements this a bit strangely. They say that you should bind a hardware nic to the software initiator, by creating two port groups on one vswitch. Then change the default path selection policy to Round Robin, esxcli nmp satp setdefaultpsp --satp="VMW_SATP_EQL" --psp="VMW_PSP_RR"

I have the following questions

• How do we confirm that multi-pathing and load balancing is really working correctly?
• Is this load balancing session based, one VM pins it’s communications to one path?
• Doesn’t the above esxcli nmp command affect the VM networking in some way?

[a_p_]

How do we confirm that multi-pathing and load balancing is really working correctly?

You can check the "Active I/O" paths for each LUN in the its properties. It can be managed the "Path Selection" in the GUI by either right clicking in "Storage Adapters" (select the appropriate vmhba and then right click the "Device") or in "Storage" (select the datastore, click "Properties" -> "Manage Paths..:") Changing between supported path policies can be done online and takes effect immediately after clicking the "Change" button.

Is this load balancing session based, one VM pins it’s communications to one path?

The load balancing is host LUN based and completely transparent to the VM.

Doesn’t the above esxcli nmp command affect the VM networking in some way?

The command is optional. It just re-defines the default settings (based on the storage vendors best practices) so you don't have to configure it for each newly presented LUN.

André