I host a number of servers in my home, many of these servers are virtualized, but of course, something physical has to exist to actually host these systems. One such physical system of mine is my NAS (Network Attached Storage). This system acts as a core server for my network, providing storage for a variety of my VMs, allowing their virtual drives to be far smaller and allowing me to increase their available capacity as simply as adding new drives to my NAS. For the past few years, I have been making use of a DAS (Direct Attached Storage) system that has allowed me to add more drives in another system and connect them to my NAS using SAS.

Until now this system has been working fine for me, however, I have recently started hosting a Plex server, and this is a workload that many will know can start to consume large quantities of storage. In order to meet the demand of this use case I have been diligently adding hard drives to my DAS, however, I have recently run out of physical space in my current DAS. As a result, I have had to get creative with my storage upgrade, resulting in modifying an existing server case to suit my needs.

In the world of server storage there are systems known as disk shelves, these are systems that can act as a DAS by connecting multiple hot-swappable drives to another remote system. These are exceedingly useful systems as they allow for quick drive replacement, are capable of being daisy-chained, and have excellent airflow to keep the drives running cool. Unfortunately, these pieces of retired enterprise hardware can be hard to get ahold of in the great white north, and when they are available it is at an exorbitant cost typically due to coming from the US. As a result, those of us outside of the US have to get tricky with our disk storage.

Before we get into the design of my system we should cover a bit of background. Most consumer-grade computers use an interface known as SATA to communicate with disks connected to them (Let's not get into PCIe today). This interface is great because it provides a fast connection between the system and the drive, however, this interface does have a limitation in that most systems have a relatively small number of SATA ports available. Of course one can add additional SATA capacity by adding PCIe SATA cards, but this will only work as long as the drives are within one system. Once you are out of space in the system for PCIe cards or drives you can't add any more. There are cards that allow for SATA multiplexing getting multiple SATA ports from one main port, but these generally don't provide many extra ports and can no be chained. The final nail in the coffin for expanding SATA is that SATA is not a standard that likes to be moved outside of a host system. eSATA does allow for external SATA connections, but is only rated for a distance of 6.6ft and would require a large number of cables to add minimal extra capacity.

After all this talk of SATA you might wonder how on earth systems with many dozens of drives work? Well, one such method is through the use of SAS or Serial Attached SCSI. SAS is an interface that is built first and foremost for the enterprise, with many features not seen in SATA. The features we will be taking advantage of today are that SAS multiplexing is much simpler and more effective, as well as its native support for being an interconnect between systems. Unlike SATA where we can only multiplex a given port once, SAS allows for daisy-chaining of multiple SAS multiplexers, meaning that the only limit to SAS expansion is the number of drives your controller can index and the reduction in speed given many iterations of daisy-chaining.

In my case, I use an LSI 9200-16e SAS HBA, this is a SAS interface card that provides 4 SFF-8088 connectors for SAS interfacing. The SFF-8088 connector is intended as an external interconnect meant to connect two SAS systems. Each SAS connector carries 4 SAS signals, meaning that my card can support 16 drives at full speed (in the case of my card this is 6gbps SAS or 3gbps SATA each). However, should I wish to make use of multiplexing my card is capable of supporting up to 512 drives at a multiplexed speed. That means that each disk is detected at the maximum speed of the slowest part of the SAS network and will only start to see speed degradation if we exceed 4 disks worth of bandwidth on a single SFF-8088 link. So by making use of multiplexers, we can get up to 4 disks worth of bandwidth over each of these connectors, and as many drives on each as we could want up to 512.

With the background out of the way it is time to discuss the hardware I have chosen for this project. I will try to provide links for the parts used, but links are subject to change as listings are taken down.

The design of this project took place over the course of about 2 weeks and all design files are available on thingiverse. Assembly of the parts is done through the use of M3 heat-set inserts and matching M3 cap head bolts. However, for the bracket faceplates, button head bolts are mandatory due to clearance with the drives. Most of these parts are attached to the case using nonexistent holes in the prints. These will have to be added either by modifying the files, or creating them as needed.

Most of the parts are unique, but together you will need 4 completed bracket bottom units, all of the bracket tops, one PCIe bracket, one each of the spacer and spacer bottom, all four drive spacers, two fan mounts, and one center fan mount. There are some issues with these designs that are noted on the Thingiverse page that are intended to be fixed in the future.

The assembly of this unit is done as follows