SAN For All - Part 2

Posted by bitbud on December 4, 2008 under How To, Rock Solid IT, SAN, Virtualization |

Picking a Path

When you think of your SAN (or any IT system, for that matter) there are two areas to address: the hardware and the software.  There are many ways to go about putting together a SAN for your environment.  Some possible options might be:

• Buy a SAN from a SAN provider: Equalogic/ Dell, Compellent, or Xiotech.
  This is your hardware and software in one package.  This will provide you with a quick, high quality solution with an easy to use interface.  You won’t even need an in-depth understanding of the technologies involved, as it is all nicely packaged for you.  The biggest barrier is usually the cost.  If that’s not an issue for you, if you are comfortable with someone else being responsible for your critical software stack, and you’d rather not get into the nitty-gritty of SANs (i.e., you want the super easy way to do it :-)), then I can point you to a brother who is a reseller.
  
• Buy a commercial application for PC/ Server hardware to turn it into a SAN.
  A good example would be the application San Melody, which I have been told works quite well.  Of course, you need the appropriate hardware, and the license is a little expensive.  Like option 1, it is nicely packaged and you don’t have to get your hands dirty with the technical details.
• Use a completely free and open source system like OpenFiler.
  This system, like San Melody, will provide you will a packaged software solution that you install on your own hardware.  It has many easy to use features.  It probably requires just a little bit more technical understanding than options 1 and 2, but it is still easy to use and best of all, its free.
• Use Linux
  … or more specifically, use Linux with a few specific packages: LVM2, iSCSI Enterprise Target, Ethernet Bonding, and (if you want to cluster, like I do) NFS.  This is what I will focus on the rest of this series of SAN articles And yes, this is what OpenFiler offers in a completely packaged system.  I’ll go into detail soon why I am not using it later.

Don’t assume that must give up some feature or functionality by using Linux.  On the contrary, for a much reduced cost you can have the equivalent system (I would argue a better system).  For me, Linux has become my Swiss Army Knife of SANs.  The same stable system can be used on low-end or high-end hardware, which keeps administrative costs down (keep it simple).  On the low-end: in Part 1 I mentioned that I built a full featured system (minus stellar performance and some hardware redundancy) for less than $500 with spare PCs and a few new hard drives. On the high-end: if you do have some money to spend on hardware, and need the best in performance and redundancy, you can purchase the same redundant hardware as a commercial SAN, same hardware warranty, for only 10%-25% of the cost!
I didn’t arrive at option 4 lightly, but after several months of investigation, testing, and consideration of these options.  There were several aspects to consider:

• Cost. The cost factor can’t be ignored.  It wasn’t the biggest reason for me, but it will be for most.  It is important to be a good steward your resources, regardless of how limited or unlimited they may be, the money spent has to be considered
• Ease of use. I’m sure some will disagree, but I don’t think having a GUI automatically makes something easier to use.  In the case of a critical component like a SAN, a GUI may simply make it easier to break.  If you think typing an e-mail is easy, and you can handle typing a few sentences from instructions, then using Linux from the command line for managing a SAN is easy too.  In fact, you could argue that typing in a command is much more precise than clicking around a GUI, and therefore could be easier to use, especially considering the importance of getting it right.
• Rock Solid IT. A SAN is about as critical a component as you can have.  All your data is congregated in one place.  It is the disk space for all your servers.  It has to run all the time with no down time - it has to work.  Period.
• Good Stewardship. Someone else will eventually need to come behind you and work on this.  You WANT others to be able to help.  I toyed with this thought for a while, as as a friend from the RT pointed out to me to make sure it was covered.  See ‘Ease of Use’ above, I think so long as you document what you have done, and how to do it, you cover the ability for someone else to pick it up.  The interface doesn’t really matter.
• Ownership. I’m an engineer.  I realize everyone in IT may not be an engineer, but for me there is a huge value add when not using a proprietary software stack.  The ability to fully own what you are using, and not be open to a company pulling the rug out from under you when you least expect it (as can happen with proprietary/ closed source offerings).  Some see the Linux/ Open Source aspect as a disadvantage, but I disagree.  True, you do need some technical knowledge, but you hopefully do, working in IT.  For me, I am the last line of support, not some vendor.  If I am responsible for a system, I should understand in 100% and be able to address any issues with it.  Others would disagree, and prefer to outsource that responsibility, and I understand how they arrive at that conclusion.  On that note, I will tell you that this IS easy to do, and if you follow good production IT principles (like testing and stabilizing production systems before implementation) you will have a system that will be Rock Solid reliable.

Here’s whats coming up in the SAN For All series:

• Specs for building a high-end, fully redundant 16 TB SAN for less than $9000
• Implementing a SAN for cheap
• Installing an iSCSI SAN - Step by step process for using Ubuntu LTS Linux as a Rock Solid SAN
  • Working with physical disks and LVM2
  • Configuring iSCSI Targets
  • Managing LVs - snapshots, resizing
• Configuring Network bonding - How to get 10Gb speed with redundancy for less
• Virtualization methodologies
• NFS for clustering, just like an HPC
• RAID configuration suggestionsUpdate: I have 3 systems running Ubuntu with the iSCSI ET now, and the performance and ease of use is great.  More to follow soon.

Note: There are other options for getting a SAN for your use.  For example, there are iSCSI Target applications that you can add to Windows to allow it to function as an iSCSI server.  My focus here is on serious, production use of SAN technology.  It has to be rock solid stable and running for years with minimal maintenance.  Moving on…