Mobile Racking A Server

The Super Microcomputer (SuperMicro) SuperServer 6046T-TUF I put together a while ago is still going strong but it had a trio of 5.25-in drive bays that were going to waste (Fig. 1). Of course, these days 5.25-in hard drives are history and even 3.5-in hard disk drives (HDD) are being used for high capacity applications. The cutting edge tends to be 2.5-in solid state drive (SSD) and HDDs.

Figure 1. The SuperMicro SuperServer 6046T-TUF has five hot swap 3.5-in drive bays and three 5.25-in drive bays.

Now I could do something silly like put a 2.5-in drive in a 3.5-in adapter inside a 5.24-in adapter or I could pop in SuperMicro’s CSE-M28 Mobile Rack (Fig. 2) instead. The rack fits into a dual 3.5-in drive bay. It is designed to work with a number of SuperMicro cases but it will fit in most other cases with sufficient space.

Figure 2. SuperMicro's CSE-M28 Mobile Rack holds eight 2.5-in SAS/SATA drives and fits into a dual 5.25-in drive bay.

There are actually two versions of the unit. The OEM unit comes without a fan on the rear. This is the one I used. The other comes with a fan but it extends out the back so it needs sufficient clearance.

Mounting the rack was an interesting exercise but rather quick because of the SuperMicro case. The case has a triangular stop (Fig. 3) for each drive bay. It is simply a matter of adding a screw to the side of the Mobile Rack, slide it in, and lock it in place.

Figure 3. Notice the back of the drive cage where there are three plastic, triangular stops. These slide out of the way to allow mounting screws on the side of units that fit into the cage.

If the rack is installed in a conventional case then it is a matter of adding screws after the rack is installed in the drive bays. Some cases have their own mounting brackets that allow the rack to slide in and lock in place.

There is one caveat for the SuperServer 6046T-TUF system. It turns out that the mounting hole alignment requires the rack to be mounted upside down (Fig. 4). That does not make a difference in connecting cables or operation of the hot swap drives.

Figure 4. Normally the rack would be mounted right side up so the alignment of the hot swap drive buttons would be the same as the 3.5-in drives on the left but the rack has to be mounted upside down.

Removal of the rack is just as simple. There is a release button that allows the rack to be removed. Of course, cabling needs to be removed first.

Filling in the Rack

The first step is add some drives to the rack. For this project I used five Seagate 15K Saviio drives. These high speed, 6 Gbit/s SAS drives are designed for high performance systems. Configuring them into a RAID 5 system provides redundancy.

Of course, these days flash storage is even faster but hard disks are still more cost effective when it comes to capacity. Some environments can afford the cost of flash storage and there are some very large systems that use nothing but flash storage. In this case we have a compromise with three slots for some Micron M500DC (see “Enterprise SSD Targets Big Data Applications”) enterprise 6 Gbit/s SATA solid state drives (SSD). The M500DC is designed for a 5 year life assuming 1 to 3 drive fills per day.

I will have a second article that will address the various configurations I tested. This includes using the flash drives as a conventional RAID system as well as using them in another configuration to cache the RAID 5 hard disk array.

The last piece to the puzzle is the Avago Technologies’ LSI MegaRAID 9361-8i. One feature that will used is the CacheCade support. This allows the controller to use flash drives to cache the contents of the hard disk drives. The CacheCade software is enabled with a small key that has to be plugged into the board (Fig. 5). More about CacheCade in the next article (see "The Joys of SSD Caching").

Figure 5. The MegaRAID CacheCade support requires installation of a small module.

The MegaRAID 9361-8i board was installed next to another LSI SAS controller that was handling the 3.5-in hard drives (Fig. 6). LSI’s MegaRAID Storage Manager can handle both although caching works within one controller.

Figure 6. The MegaRAID 9361-8i board (right) was installed next to another LSI SAS controller (left) that was handling the 3.5-in hard drives.

The one thing to keep in mind is getting cables with the proper connectors on each end. The version I have uses the old Mini-SAS SFF8087 connectors. The newer version of the SuperMicro mobile rack that has 12 Gbit/s SAS-3 support has the newer Mini-SAS SFF8643 that are also found on the MegaRAID 9361-8i board.

The hardware installation actually goes rather quickly. The most time was taken up with installation of the HDDs and SDDs in the hot swap drive trays. Plugging in the MegaRAID 9361-8i and cables takes just a few minutes.

The mobile rack works with any controller. Another alternative for this configuration would be to use a SAS expander and connect it to the existing SAS controller. A SAS expander is typically found in disk racks with dozens of drive bays. A single SAS connection is needed between the SAS controller and these systems. SAS expanders normally have a lot of connections so one could handle multiple mobile racks.

I am off to checking out the MegaRAID Storage Manager (MSM) software.