Contoso Labs-Storage Purchasing (SAS config)

Contoso Labs Series – Table of Contents

Now that we’ve got our JBODs and our file servers, we need to tackle an underappreciated aspect of this solution: The SAS connectivity itself.

How Many?

After discussing our configuration and layout with folks inside of Microsoft with serious experience in Storage Spaces, we learned that having as much connectivity to our JBODs as possible was going to be the ideal configuration. Our planned SOFS cluster was 3 file servers with full connectivity to 3 JBODs. Each JBOD has dual controllers, each controller with 3 SAS ports. That meant we could provide full dual-path access from each server, to each JBOD, for a total of 18 connections.

In practical terms, that meant we needed six external SAS ports in each file server. That started limiting our options for SAS controllers. There are many 2-port cards out there, and a smaller selection of 4-port ones. No one makes a 6-port card. That meant we were definitely going to need to commit both of our PCIe slots to SAS controllers. We briefly considered a 4-port and a 2-port card, but decided that consistency and symmetry were useful here. One driver, and losing a card loses 1 path to each JBOD, instead of potentially losing all access to 1 of them. We chose cards from LSI for our solution.

LSI

We selected LSI 9206-16e cards for our SAS connectivity. These cards checked all the right boxes for us.

  • They’re certified for use with Storage Spaces.
  • They have 4 external SAS ports each.
  • DataON supports them with their JBODs.
  • They’re half-height PCIe cards, which means they work in both slots of our servers.

The only drawback we could find with using these cards is that they have SFF-8644 connectors on them. These are lesser-used small form factor connectors than the more well-known SFF-8088 type you might be familiar with on most SAS equipment. The smaller size means 4 ports can fit comfortably on a half-height card, where the larger SFF-8088’s would be too large. That meant getting specialized cabling, a minor hassle at worst.

Now that we have all the pieces of our storage puzzle identified, we can build out some file server clusters and get down to business, right? Well, not quite yet. When time comes to put everything together, we’ll have a lot more information about our storage configuration, and some information about how it’s all working. Next up, we’ll circle back to our purchasing decisions, specifically the network gear.