My new database server (Windows Server 2008 R2) has a 4 Gbps connection to my Dell EqualLogic iSCSI SAN. I've been testing it by backing up multiple databases at the same time. There appears to be a bottleneck with the network adapter. It shows up as 4 1 Gbps connections, and the network utilization never exceeds 2 Gbps. Any recommendations where to look next?

SAN: 48 drives. 10K 600GB SAS. Raid 50.


Flow control is set to auto, but I think it is being used because MPIO is installed. There is a switch and I'm working on jumbo frames, but while researching MPIO I noticed something that might be affecting performance.

In the database backup test I was performing, 4 volumes were involved: one for data, one for the log, and 2 for the backup files (split by RedGate SQL Backup to improve performance). I was trying to determine if there was any performance benefit to separate volumes on a SAN. On my old server, I would use 4 different RAID arrays in this situation.

Each of my 1 Gbps network adapters has an IP assigned in the range Each volume has 2 of these IP addresses assigned to it in the "Dell EqualLogic MPIO" tab in iSCSI Initiator Properties. 251 & 252 are used for the log & both backup volumes. 252 & 253 are used for the data volume. It seems like this could be a limiting factor.

I'm going to see if I can assign them different IP addresses.

Update 2:

Using the MPIO Remote Setup Wizard, I changed the "Max sessions per volume slice" from the default 2 to 4 and rebooted. Each volume now has 4 paths, one for each NIC. The utilization is now fairly evenly distributed between the 4 NICs, but the total is still less than 2 Gbps. Each one maxes out at about 45%. Once I get access to my switch I will try to get jumbo frames working and see if that helps.


Jumbo Frames. They had to be set on the database server NICs and on the switch. The SAN handled it automatically. This required a reboot on the DB server.

  • 3
    How did you connect? MPIO? Etherchannel? Why do you think that it is the connection which is saturated and not your array's I/O capabilities?
    – the-wabbit
    Sep 26, 2011 at 16:49
  • I have to admit I'm a newbie when it comes to some of this. I assumed that it was not the I/O because the "SAN HeadQuarters" tool from Dell indicated that the Estimated I/O Load was "Medium" during the backup. Sep 26, 2011 at 17:22
  • 3
    Sounds like a 6510, are you passing through a switch? Did you install the MPIO drivers from Dell? Did you configure the NICs on your server for jumbo frames? Sep 26, 2011 at 17:35
  • These are all good questions. I will look into this and post my results. Sep 26, 2011 at 19:10
  • 1
    The four Equallogic NICs will each have an IP address, and any one of them can provide any volume (providing ACLs allow this). Since this is going to a switch, and you have four network connections on your server as well, then you should see four paths to each volume. Sep 26, 2011 at 20:59

1 Answer 1


What kind & how many hard disks does your SAN have? 2Gbps is around 250MB/sec which is very decent performance if you have a pretty large array of 7200rpm SATA drives.

If you need higher performance you should look into equipping your SAN with SSD disks which offer higher I/O.

  • I have added the disk info to my question. Sep 26, 2011 at 17:27
  • Hmm OK then disk I/O is not your problem apparently :) Sep 26, 2011 at 17:41
  • 1
    Do you have Jumbo Frames, Flow Control, etc setup on your NICs and the Switch connecting the EqualLogic Array? Sep 26, 2011 at 17:47
  • I will look into this. Sep 26, 2011 at 19:13

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