As mentioned in my articles on building a custom server case and the iSCSI Enterprise Target on RedHat Enterprise Linux 5.3, sometimes there is the need to facilitate stiff project requirements while spending nearly nothing. In a booming economy, it is unlikely that you would need to create your own production/enterprise worthy SAN environment. There is a reason a SAN is so expensive, even without the expensive SAS drives; it’s called engineering and manufacturing!
This article discusses issues I have come across while building or testing opensource iSCSI target software with various iSCSI initiators. I began testing the IET product on Ubuntu Server 8.04 with VMware ESXi 3.5, which worked well in a segregated lab. Then I moved forward to testing a “production” IET target with Microsoft’s iSCSI Software Initiator, which also worked exceptionally well. Finally, I moved into the VMware ESX 3.5 realm, which did not go well at all, initially.
Test 1: VMware ESXi 3.5 and Ubuntu Server 8.04, iSCSI Enterprise Target (IET)
The test was a combination of feasibility and reliability, with an emphasis on the feasibility aspect. For the Ubuntu Server that served as an iSCSI target, I used an older 1U Dell PowerEdge 850 server. The network fabric was a HP ProCurve 48 port switch, which was used for both the standard network environment in the lab and the iSCSI network.
The test went well with a new VM build to the iSCSI target of Windows Server 2003. Heck yes. The feasibility was there as it took an afternoon to make it happen. The reliability was also there, especially since everyone touts Linux as the most solid operating system in the world.
Test 2: Microsoft iSCSI Initiator and IET
Although I am a Microsoft guy by trade, when it comes to new technology I am generally weary of Microsoft’s implementation as a solid product. However, during my testing of the iSCSI Enterprise Target (IET) opensource target software (0.4.17), I have had absolutely no issues or concerns. After testing in a production lab environment, we moved to testing with our backup to disk project. In this instance, the iSCSI target is used for backups to disk and is hammered almost 24/7 by EMC Retrospect through the Microsoft iSCSI Software Initiator. The product has been running strong for 3 months as of 8/1/2009.
Test 3: VMware ESX 3.5 to 4.0 and IET
If you notice the title of this third test, you may gather that the initial testing did not go as well as was anticipated. In fact, I had a heck of a time getting the ESX 3.5 software iSCSI to even see the IET target from the start. At first I though the configuration was invalid, however, the Microsoft iSCSI Software Initiator worked exceptionally well with the same target with no reconfigurations.
To FINALLY get to a semi-solid state, I began with simplification…
As this was the third test, following two successful tests, I decided that I would enter the test with more features enabled, such as multipathing or bonding. This ended up over-complicating the project as there are some known issues with multipathing IET with VMware. To help resolve the issues with connectivity and failures, I went back to one gigabit link, no bonding or multipathing.
Upgrade ESX host from 3.5 to 4.0
Following a technical support call with VMware, I decided to upgrade ESX to vSphere 4. The technical support person wanted me to update ESX 3.5 to the latest build, so I figured, let’s jump to the next level (should I have revisited “simplify”??).
Immediately following the ESX 4.0 installation, I was able to see the iSCSI LUNS. However, I was not able to use them as I kept receiving an error message about not being able to get disk information. If I remember correctly, this was resolved by using “blockio” type on the IET LUNs instead of “fileio”.
Modify IETd.conf to match ESX iSCSI settings
This change was to ensure that the VMware iSCSI software initiator shared the same “mindset” as the IET target. If I remember correctly, only ESX 4 hosts can modify the iSCSI initiator settings.
After running into a list of complexities getting IET to work well with VMware, I finally got it to play nicely for almost 2 weeks. And then…I received the an “unknown command” error in /var/log/messages and the IET target software jammed up causing the VMware virtual machines to lock up.
From my perspective, enough time has been given to IET and I do not feel as though it is ready for VMware – or that VMware is ready for it. I am, therefore, moving forward with OpenSolaris for two reasons, built in iSCSI target and ZFS. More to come…