Advise required for Software SAN Network and VM Network on the same host

[crescendas]

If I have a software-base SAN running on the same physical ESX host with some VMs, and I have place the sofware SAN iSCSI on the Storage Network (Network card 1) and the VMs on the VM Network (Network card 2).

When the VMs want to access iSCSI drive on this SAN storage, will ESX be smart enough to know that both are on the same physical host and switch to direct SATA/SCSI harddisk cable transfer? Or will it still transfer the data thru the 2 network cards to reach both destinations?

If ESX isn't smart enough to bypass for direct path, will placing these VMs that are running from iSCSI on Storage Network instead of VM Network improve the transfer rate?

Thanks

[AntonVZhbankov]

If all VMs are on the same host, try to enable VMCI for all of them - that would provide you a kind of bypass.

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MCSA, MCTS, VCP, VMware vExpert '2009

http://blog.vadmin.ru

[crescendas]

Thanks for replying. Does this mean that ESX is not smart enough to bypass the network port despite the data transfer is within the same harddisk?

And since I do have other physical hosts accessing to this Software SAN, does this mean that your suggestion of enabling VMCIfor all the VMs should not be done in my case?

Thanks.

[Texiwill]

Hello,

Thanks for replying. Does this mean that ESX is not smart enough to bypass the network port despite the data transfer is within the same harddisk?

If you setup iSCSI/NFS it will send all traffic over the vSwitch as they ARE network protocols not direct SCSI protocols. It does NOT transfer data over the local storage until the software 'SAN' is writing the data..... I.e VM<->vSwitch<->bridge<->vSwitch<->iSCSI Server<->Write to physical disk

And since I do have other physical hosts accessing to this Software SAN, does this mean that your suggestion of enabling VMCIfor all the VMs should not be done in my case?

VMCI is not of much benefit here as the Software SAN would need to be programmed to make use of VMCI for transferring packets and the VM would have to have a driver that when you wrote to iSCSI detected VMCI and used it. Neither of these exist.

Best regards,
Edward L. Haletky VMware Communities User Moderator, VMware vExpert 2009

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