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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.

Update:

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 10.0.1.251-10.0.1.254. 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.

Solution:

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.

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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 '11 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. –  Keith Walton Sep 26 '11 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? –  SpacemanSpiff Sep 26 '11 at 17:35
    
These are all good questions. I will look into this and post my results. –  Keith Walton Sep 26 '11 at 19:10
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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. –  SpacemanSpiff Sep 26 '11 at 20:59
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1 Answer

up vote 3 down vote accepted

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.

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I have added the disk info to my question. –  Keith Walton Sep 26 '11 at 17:27
    
Hmm OK then disk I/O is not your problem apparently :) –  George Tasioulis Sep 26 '11 at 17:41
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Do you have Jumbo Frames, Flow Control, etc setup on your NICs and the Switch connecting the EqualLogic Array? –  George Tasioulis Sep 26 '11 at 17:47
    
I will look into this. –  Keith Walton Sep 26 '11 at 19:13
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