Random Half Thoughts While Driving

So I often have epiphany teasers while driving long distances or stuck in traffic. I call them teasers because they are never fully developed ideas and often disappear into thoughts about passing cars, or yelling at the person on their cell phone going 15 MPH taking up 2 lanes.

Here is some I was able to save today (VMware related):

1. What if I DID want an HA cluster to be split in two different locations, Why?
2. Why must we over-subscribe iSCSI vmkernel ports to make the best use of the 1gbe phyical nics. Is it a just the software iSCSI in vSphere? Is just something that happens with IP storage? I should test that sometime…
3. If I had 10 GB nics I wouldn’t use them on Service Console or Vmotion that would be a waste. No wait, VMotion ports could use it to speed up  your VMotions.
4. Why do people use VLAN 1 for their production servers? Didnt’ their Momma teach em?
5.  People shouldn’t fear using extents, they are not that bad. No, maybe they are. Nah, I bet they are fine, how often does just 1 lun go down. What are the chances of it being the first lun in your extent? Ok maybe it happens a bunch. I am too scared to try it today.

VMware View and Xsigo

*Disclaimer – I work for a Xsigo and VMware partner.

I was in the VMware View Design and Best practices class a couple weeks ago. Much of the class is built on the VMware View Reference Architecture. The picture below is from that PDF.

It really struck me how many IO connections (Network or Storage) it would take to run this POD. Minimum (in my opinion) would be 6 cables per host with ten 8 host clusters that is 480 cables! Let’s say that 160 of those are 4 gb Fiberchannel and the other 320 are 1 gb ethernet. The is 640 gb for storage and 320 for network.

Xsigo currently uses 20 gb infiniband and best practice would be to use 2 cards per server. The same 80 servers in the above cluster would have 3200 gb of bandwidth available. Add in the flexibility and ease of management you get using virtual IO. The cost savings in the number director class fiber switches and datacenter switches you no longer need and the ROI I would think the pays for the Xsigo Directors. I don’t deal with pricing so this is pure contemplation. So I will stick with the technical benefits. Being in the datacenter I like any solution that makes provisioning servers easier, takes less cabling, and gives me unbelievable bandwidth.

So just in the way VMware changed the way we think about the datacenter. Virtual IO will once again change how we deal with our deployments.

iSCSI Connections on EqualLogic PS Series

Equallogic PS Series Design Considerations

VMware vSphere introduces support for multipathing for iSCSI. Equallogic released a recommended configuration for using MPIO with iSCSI.   I have a few observations after working with MPIO and iSCSI. The main lesson is know the capabilities of the storage before you go trying to see how man paths you can have with active IO.

  1. EqualLogic defines a host connection as 1 iSCSI path to a volume. At VMware Partner Exchange 2010 I was told by a Dell guy, “Yeah, gotta read those release notes!”
  2. EqualLogic limits the number of hosts in the to 128 per pool or 256 per group connections in the 4000 series (see table 1 for full breakdown) and to 512/2048 per pool/group connections in the 6000 series arrays.
  3. The EqualLogic MPIO recommendation mentioned above can consume many connections with just a few vSphere hosts.

I was under the false impression that by “hosts” we were talking about physical connections to the array. Especially since the datasheet says “Hosts Accessing PS series Group”. It actually means iSCSI connections to a volume. Therefore if you have 1 host with 128 volumes singly connected via 1 iSCSI path each, you are already at your limit (on the PS4000).

An example of how fast vSphere iSCSI MPIO (Round Robin) can consume available connections can be seen this this scenario. Five vSphere hosts with 2 network cards each on the iSCSI network. If we follow the whitepaper above we will create 4 vmkernel ports per host. Each vmkernel creates an additional connection per volume. Therefore if we have 10 300 GB volumes for datastores we already have 200 iSCSI connections to our Equallogic array. Really no problem for the 6000 series but the 4000 will start to drop connections. I have not even added the connections created by the vStorage API/VCB capable backup server. So here is a formula*:

N – number of hosts

V – number of vmkernel ports

T – number of targeted volumes

B – number of connections from the backup server

C – number of connections

(N * V * T) + B = C

Equallogic PS Series Array Connections (pool/group)
4000E 128/256
4000X 128/256
4000XV 128/256
6000E 512/2048
6000S 512/2048
6000X 512/2048
6000XV 512/2048
6010,6500,6510 Series 512/2048

Use multiple pools within the group in order to avoid dropped iSCSI connections and provide scalability. This reduces the number of spindles you are hitting with your IO. Using care to know the capacity of the array will help avoid big problems down the road.

*I have seen the connections actually be higher and I can only figure this is because the way EqualLogic does iSCSI redirection.

Five Things you should know about VMware Certification – thanks @rickvanover

Tonight I was sitting with my Mac Book Pro, wife and kids all in bed, perfect blogging time. Except no idea what I wanted to write. After a burst of twitter encouragement from @rickvanover here we go:

Five things you should know about VMware Certs:

1. If you work for a VMware partner, start with the VSP/VTSP Certifications. They require a lot less initial investment and give you the start into VMware products. Partners only.

2. You can take the “Install and Configure” or “Design Secure and Analyze” or the “Fast Track” (which is some kind of combo of the previous 2) then study and take the VCP. The VMware Certified Professional is the standard in Virtualization industry and has personally opened many doors for me professionally. VMware Partners NEED them, but it is quite an investment. The class is far from free and the test isn’t cheap. Something to know though, if you go to VMworld the tests are discounted. So everyone at VMworld take advantage! Save a few bucks.

3. As good as the VCP is, there is still a demand for VMware knowledge more advanced than the base cert. I lost my job last year, while job hunting I saw listings asking for VCDX certified people. At the time no VCDX’s were publically known. It just shows the demand for proof of advanced knowledge in VMware and a possible dilution of the VCP due to brain dumping.

4. Testing experience is fairly standard technical testing. Although I wish it was all lab practical rather than memorization. Multiple choice type questions are the majority of the questions. My best test taking tip is to actually know how to Install and Manage Virtual Infrastructure. You can run it all in VMware Workstation 7, so there is no excuse to just memorize answers. I say that but you will have to memorize max and minimums and other facts in order to pass the VCP.

5. Check what is on the blue print on the VMware Certification website, this website is the final word on what is on the test.

Bonus: Use the communities/blogs/twitter to find information and answers. Don’t just post “Hey what is on the exam?”. Ask questions about technical topics, then make sure you could articulate the concept to someone else. I find if I understand enough to be able to teach it to someone else then I really am starting to learn things.

Bonus #2: Be willing to be always learning. If you already know everything you probably don’t need the certification.

*No clue who the original artist is of that picture. It is awesome, so if you know who to credit let me know.