Storage Pod 4.5: Tweaking a Proven Design

It has been nearly a year since we published an update to our Storage Pod design. Over the last few months we have been deploying Storage Pod 4.5, which is known internally as Storage Pod Classic. The reason for the “classic” nickname comes from the fact that Storage Pod 4.5 is derived from our Storage Pod 3.0 chassis and design. Storage Pod 4.5 returns to the backplane-based design of Storage Pod 3.0 but incorporates upgrades that improve reliability and reduce cost. The result is that Storage Pod 4.5 delivers 180TB of data storage for only $0.048 per gigabyte, our lowest cost ever.

What’s New in Storage Pod 4.5

Storage Pod 4.5 is built on the same chassis as Storage Pod 3.0, but with an upgraded parts list. The upgraded items are:

• Backplanes
• SATA cards
• CPU

To the delight/dismay of many in the Reddit community, we did not change the on-off switch.

Back to Backplanes

One of the principle design decisions we made in Storage Pod 4.5 was to return to using five-port SATA backplanes versus the direct-wire design of Pod 4.0. We’ll dig in to why we returned to backplanes a little later in this post, but for the moment let’s cover the backplanes we are using in Pod 4.5.

At the core of the new backplanes is the Marvell 9715 chipset. Over the years, Marvell has proven to be committed to the storage market and manufacturing the chipset fits nicely into their business. Both Sunrich and CFI use the 9715 chipset as part of their five-port backplanes. We now have a backplane that is readily available, well supported and faster with 6 Gbps SATA-3 throughput.

New SATA Cards

For Storage Pod 4.5 we upgraded to SATA cards manufactured by Sunrich using the Marvell 9235 chipset. The same chipset is also used by SYBA in their latest SATA cards. When combined with the upgraded backplanes, the new SATA cards deliver 6 Gbps SATA-3 throughput.

Upgraded CPU

The CPU was upgraded from an i3-2100 to an i3-2120. The i3-2100 has been EOL’d by Intel and the i3-2120 delivers slightly better performance for the same price. We’ve also tested the i3-3240 and it worked fine. Other LGA 1155 socket CPUs should work as well, although we have not tested any beyond those mentioned.

Storage Pod Costs

Storage Pod 4.5 is less expensive to build and fill with hard drives than all its predecessors. The entire system, fully populated with 180TB worth of hard drives, costs Backblaze less than a nickel per gigabyte. With larger capacity hard drives now coming to market, the cost per gigabyte for hard drive storage should continue to decrease and drive down the cost of each Storage Pod we build. This will allow us to continue to charge just $5/month for our unlimited online backup service.

Below are the Backblaze costs for building the different Storage Pod versions.

Building your own Storage Pod or having a Storage Pod built for you will likely cost somewhat more, but the cost of the hard drives will continue to be the main cost component.

Our Round Trip to Backplanes: The Inside Story

Each month Backblaze needs to build and deploy 20 to 30 Storage Pods. To do this, we employ a contract manufacturer to bend the metal and assemble the parts into a Storage Pod that we load test and qualify before placing into service. Backblaze then monitors and maintains the active Storage Pods. Prior to Storage Pod 4.0, we had built and deployed nearly 800 backplane-based Storage Pods.

Two unrelated events drove our decision to go down the direct-wire design of Storage Pod 4.0. First, we had a dwindling supply of five-port backplanes as Silicon Image stopped making the chipset used to manufacturer the backplanes and second, our existing contract manufacturer was having trouble meeting our production schedule for Storage Pods.

Into the breach stepped Protocase. Over the years, they have been a huge Backblaze Storage Pod supporter and created their 45 Drives division to sell Backblaze-inspired storage servers. Protocase started building version 3.0 Storage Pods for us and when we decided to go with the direct-wire design described in the Storage Pod 4.0 blog post, we used Protocase as our primary contract manufacturer.

With Storage Pod 4.0 being a completely new design, we had expected there to be growing pains. Indeed, looking back at Storage Pod 1.0, it went through multiple versions before it was ready for an operational environment. For Storage Pod 4.0, Protocase diligently worked with us over the course of several months to address the growing pains and get Pod 4.0 systems deployed in our data center.

While we worked to get Storage Pod 4.0 ready, we still had to deploy 20-30 operational Storage Pods each month. After testing out several local contract manufacturers, we found Evolve Manufacturing. They were eager, smart, located nearby, and proved to be excellent at building Storage Pods. At the same time, new vendors stepped forward with five-port backplanes and SATA cards based on the Marvell chipsets. This meant we had everything we needed to go back to the future and build backplane-based Storage Pods to meet our operational needs, and that’s what we did.

Late last year, we finally made the decision to stop investing in the direct-wire design of Storage Pod 4.0 and proceed with upgrading our backplane-based design, and Storage Pod 4.5 was born. To date, we have deployed nearly 100 Storage Pod 4.5 systems.

What Should You Buy?

If you are looking to purchase a storage server inspired by Backblaze, here a couple of vendors we recommend:

Evolve Manufacturing: They are our supplier of Version 4.5 Storage Pods. They will sell you a fully assembled Storage Pod 4.5 chassis (without drives), a Storage Pod 4.5 kit (unassembled, no drives), or just a Storage Pod 4.5 metal chassis.

Protocase: They helped design Version 4.0 and prior Storage Pods. They also supplied Version 3.0 and Version 4.0 Storage Pods for Backblaze. Please check out www.45drives.com to see the wide variety of products they offer inspired by Storage Pod 4.0 and prior designs.

[9-1-2015 – Updated Storage Pod Supplier Information – Editor]

Making a Storage Pod

If you are inclined to make your own Storage Pod, we’ve included a list of the parts you’ll need in Appendix A. Most of the parts can be purchased online via Amazon, Newegg, etc. Some parts, as noted on the parts list, can be purchased through either a distributor or from one of the contract manufacturers. Since Storage Pod 4.5 is similar to Storage Pod 3.0, you can still use this nice screen shot assembly walk-through from Protocase and it’s companion Storage Pod assembly overview (PDF, 1.5MB) for guidance.

As a reminder, Backblaze does not sell Storage Pods and the design is open source so we don’t provide support or warranty for people who choose to build their own Storage Pods. You can find fellow Pod builders at www.openstoragepod.org and www.45drives.com/community.

Appendix A: Storage Pod 4.5 Parts List

Below is the parts list for building Storage Pod 4.5. The price shown is the current list price of the items needed to build one Storage Pod. You may be able to find a lower price for some of these items.

Notes:

• Purchase from Evolve Manufacturing for price listed, plus tax, packaging, handing, and shipping.
• Sunrich and CFI make the recommended backplanes and Sunrich and Syba make the recommended SATA Cards. These items may be purchased via Arrow (a distributor) or Evolve Manufacturing.
• Nippon Labs makes the recommended SATA cables. They may be purchased from Evolve Manufacturing.
• The Boot Drive can be any 2.5 or 3.5 inch internal drive.