iSCSI vs. USB - Why is USB faster most of the time?

We have about 12 Drobo Pro units across our customers. These are connected to dedicated Gbit NICs on our vSphere management servers for the purpose of storing Veeam backups on. Our backups have been horribly slow compared to the performance we saw previously with regular USB hard drives. I ran a test backup on two different customers with it connected via USB instead of iSCSI and it cut hours off the backup. I was under the impression that iSCSI should be substantially faster than USB with a DroboPro. Amy I mistaken?

Most of the Drobo Pro are configured with 8 x 2TB WD Green. The units are connected to the Broadcom or Intel 1000Mbit NICs in Dell 2850/2950 servers or similar. Latest iSCSI initiator is loaded on the systems along with latest Drobo software and Firmware. Drobo’s are static IP’d to a dedicated subnet used just for the Drobo.

Any thoughts?

iSCSI should be significantly faster than USB.

How are the Drobo Pro units connected to each other?
Does each Drobo Pro connected to a dedicated server, or are they connected to a switch?

These are separate units at separate clients and networks. They have no relation to each other except that proving it in more than one place convinces me that its not coincidence.

Which version of VMWare are you running 3.5 or 4.0?

Do you have VM’s on the pro’s and if so, how many?

We have at least 2 clients using Veeam Backup and FastSCP 4.x on their Windows Server 2008R2 64-bit w/ the Pros via iSCSI (cross over cable) and the throughput is acceptable and noticeably faster than USB 2.0. I suspect the bottleneck is the network switch and/or the Veeam Backup server and I recommend to give the latest version 5.0 Enterprise a try and use a 64-bit core instead of 32-bit, including the SQL.

Agreed - my drobopro is probably at least twice as fast over iscsi compared to USB

These are DroboPro units directly connected to the NIC on the server. There is no switch at all. If the server and/or software was a bottleneck it would not be faster over USB. I’ve found iSCSI faster for normal file access and IOPS sensative operations, however it seems that manipulating files in the 400-800GB range is different. That bothers me particularly in the sense that normally large files are terrible over USB. Drobo support is useless for performance related issues like this and I hoped that others might chime in here with similar results.

i only tend to deal with files which are 20-40GB each on my pro (but batches of them - so i’ll be moving maybe 300-400GB at a time), and the iscis throughput dwarves USB

@cgreentx Do you have an open case with support? If so, what is the case number?