inSANity, revealed

This past year, I decided that it was time to explore additional ways to start handling storage.  One of the items I never liked was when I run out of DAS space, I need to pull the drives, migrate the data, then put the two on the shelf to sit until they are needed.  That is a good amount of wasted disks just sitting not being used.  Then there is the issue of migrating data from old to new servers.  (Not to mention no real DR ability if there was a “catastrophic event” in our server room.  Aside from the data end of it, there also is the emerging virtualization on OS X and I wanted to have a framework in place for that so as new services were being added, we may be able to use the SAN to supplement and store the VM.  (Think snapshots here …)

Being a Mac school district, this posed some challenges since the cost of FC is a bit out of our range and would not really provide the expandability I wanted.  While there were only two servers at the moment that needed connectivity, I wanted to be able to grow that and have the capacity to expand and include other services and services down the road.  So, iSCSI was the way I was going to go.  But, try looking for iSCSI on OS X … I dare you.  There are not a lot of products and companies who have a 3rd party solution and will say “This works with OS X”TM

I began asking around to individuals in the Windows world what they were using and a friend I know out in Colorado had experience with a product.  Seeing that the town of Castle Rock, CO was using a product for Fire, Police and other municipal services, it sounded like a reliable product.  (Thanks Mike!)

Flash-forward to the actual acquisition.  Two NSM-2060’s (replaced this year with 2060 G2 units provided us with a simple 3TB RAID5 hardware setup with a network mirror.  This allows not only one drive to fail in a storage module, but also an entire module to fail without service interruptions.  Additionally, it moved a copy of our network data to another location.  This is the protection against that “catastrophic event”.

There are two products out there on OS X that work as iSCSI initiators on OS X client and server.  One, provided by Atto ( is a pay-product.  Another, by Studio Network Solutions ( is a free product.  Both worked well.  Atto’s tech support was great and SNS has some really good user-drive support forums.

Right now we have 4 volumes being used for our SAN.  One is for student data, one is staff, another is for our backups (until I work and understand volume snapshots) and the final is for our District Office data.  The volumes are shared via AFP, and a few also have SMB sharing enabled for our Windows users.  I have not had any issues with performance, which is great.

The iSCSI modules themselves sit on a separate vlan and this helps with network performance.  Each module is bound using 802.3ad and provides not only link-redundancy, but also increased bandwidth.   In our case, we have 802.3ad setup on each storage module, the switch ports to the storage modules and to one of our servers.  In that case, a 2Gbps is achievable from the SAN to that server.

The modules use a virtual IP (vIP) so that the fastest responding module will get the traffic.  This helps with latency and also works very well for upgrades.  Since a vIP is used, upgrades could be performed during the day with zero downtime.  However, there would be a data re-synch and that would result in a performance delta during that point.

Overall, the unit has been reliable and a great investment.  Thinking how it will start to play a role down the road in our infrastructure is very exiting.

A tough area is justifying a purchase that will cost much more than buying a few hard drives, but the flexibility is where you see the ROI.  When I began to list the pro’s and cons, the con was the price, but the pro’s I came up with were:

  • Flexibility in storage size allocations
  • Ability to grow volumes if more storage is needed.
  • Full copy of data at another physical site for DR.
  • Snapshots of volumes to change daily differential backup process.
  • Lays a foundation for virtual services.
  • Not limited by number of open bays in server.
  • Uses existing infrastructure

When looking at a product of this type, make sure it is a good fit, and you have ideas in place as to how you will continue to leverage the device.  Based on the price-tag, it is not a great solution for just adding storage.  But, when you start investigating and planning services that can benefit from shared storage, you can realize cost savings in hardware (maybe you buy two or three small HDs in a server for OS protection).  Keep in mind, as it is software for initiators, CPU cycles will need to be used.  Make sure your server is not over-taxed!

Questions?  Comments?  Use the comments below to post them and I will respond.


One response

16 02 2009
Talking about a SAN « Technology in Education Geekery

[…] Read about it in inSANity, revealed […]

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