We have reviewed a few smaller capacity SATADOM modules but now it is time to look at one of the largest, the Innodisk SATADOM-ML 3ME3 V2 256GB SSD. While typical SATADOM modules are 8-128GB, this one packs a full 256GB into a drive that sits just above a motherboard SATA slot. SATADOM modules have become extremely popular over the past few years, and for good reason. The form factor is easy to integrate into servers. With a growing market, there are a number of vendors vying with SATADOM designs. In this article, we are going to provide benchmarks of the Innodisk module and show how it performs compared to a few other options.
Innodisk SATADOM-ML 3ME3 V2 256GB What is it?
A SATADOM is, at its simplest, a small SSD. These SSDs are made to fit into 1U form factor servers and add an SSD without requiring a drive bay. SATADOM devices are tiny and only slightly larger than the size of a US quarter. The 256GB capacity form factor is significantly larger than the 64GB and 128GB modules we recently tested. That extra capacity can be extremely helpful if you are trying to run a Windows Server 2016 installation or need to have more space on an embedded edge device.
Key use cases for the SATADOMs are in embedded applications and as boot devices. For example, they are popular in smaller servers to reduce the overall server footprint and power consumption. For storage servers and virtualization servers, they are often used as OS drives in order to conserve drive bays for use by larger capacity disks. While OEMs such as Dell may use SD cards to boot ESXi, many other OEMs utilize SATADOMs.
Typically due to space considerations, SATADOMs do not use local DRAM caching. That lowers write performance, which as we will see is less of an issue for these drives. It also means that without a write cache, there is no need for the extra PCB space for power loss protection circuitry nor a DRAM chip. That keeps the form factor extremely compact.
One word of caution. We have spoken to a number of server manufacturers and the primary cause of failure in SATADOMs is not device failure. Rather, it is using these devices for the wrong purpose. Apparently, some MSPs have been using SATADOMs as read/ write caches for ZFS, Ceph and other storage platforms. That causes heavy writes to usually smaller capacity drives (256GB SATADOMs are considered large by today’s standards) not rated for that level of endurance. As a result, 16GB SATADOMs are incorrectly put into large storage servers with 7DWPD workloads and fail quickly. This is apparently a common issue, so STH readers, please do not try this even though a 256GB module should fare better than smaller modules due to more NAND onboard.
SATADOMs like the Innodisk SATADOM-ML 3ME3 V2 256GB have wide environmental operating ranges and are very durable. You can see detailed specs on the Innodisk website. That makes them well suited to embedded applications.
Innodisk SATADOM-ML 3ME3 V2 256GB Power and Power Consumption
In embedded platforms as well as many storage servers, there are no extra SATA power cables or Molex connectors in the chassis. That means to power a SATADOM one may require a different approach. Supermicro enables SATADOMs extensively, and the Innodisk SATADOM-ML 3ME3 V2 256GB drive is able to use a feature it calls “8 pin power” to power the SATADOM. To use this feature, you will want to utilize the gold SATA connectors on Supermicro motherboards as shown here:
In that setup, power is provided by the SATA connector itself and no additional cables are needed (see installation above.) This is a very elegant solution and is something that not all SATADOMs support. Innodisk specifically advertises Supermicro compatibility and one can see why.
If you do not have SATA connectors that support this power, you can still utilize SATADOMs. Our test units came with SATADOM power connectors as well as a 4-pin Molex power cable.
If you have never installed a SATADOM power cable onto a motherboard, the experience is generally less than pleasant as the standard headers are extremely small. If you can, always use 8-pin powered SATA ports. Here is what it looks like if you use one of the white SATA ports with a cable:
As you can see, there is the extra wire. Also, Supermicro and a few other vendors do specifically make powered SATADOM ports with extra clearance around them so you can use multiple modules. You can see that we can fit two modules on the gold ports but only one between the two white ports that are made for standard SATA cabling.
We took a few different solutions and wanted to show our system’s boot power. The Innodisk SATADOM-ML 3ME3 V2 256GB drive, despite the higher capacity, does not add an appreciable amount of power consumption to the system:
While in larger storage servers, the primary benefit is going to be the ability to use a SATA boot device without using a drive bay, the benefit on embedded systems can be more drastic. If you use SATADOMs on sub 100w nodes and then have 100 per rack, you can essentially get enough power to add two additional nodes per rack. With 256GB capacity, this can take the place of many SATA SSDs in a system not just for booting but also running applications.
Innodisk SATADOM-ML 3ME3 V2 256GB Performance
Given that we wanted to make this a larger series, we wanted to develop a methodology that makes sense. Since the typical usage of a SATADOM is to boot into an OS. Typically heavy logging and data serving will happen from other devices or network storage.
Here are the raw throughput figures using sequential writes. We are using two low capacity Intel SSDs for the comparison group.
Although SATADOMs are slower than larger SSD counterparts in terms of raw sequential write speed, the 256GB drive performs very close to the larger drives in terms of access times, It also has appreciably better read performance than the smaller SATADOMs. A lack of onboard DRAM cache slows write performance but also means that in-flight data is not cached in DRAM, which is what you want for data protection purposes. While that test may be informative into raw specs, we wanted to look at how it translates into real-world usage.
We decided to setup a test image based on Centos 7.3 to serve as a KVM hypervisor. We timed from when the server started booting to when we hit the CentOS login prompt. That should be a good proxy for performance whether you are using VMware ESXi, RedHat Enterprise Linux, Ubuntu, Debian, Microsoft Hyper-V Server, Microsoft Windows Server or other OSes. While the boot times may differ in their values, the tasks are largely the same so relative performance is what we are looking to gauge.
Here, the SATADOM solution was extremely close to the Intel S3500 SSD, with the added benefit of an easier-to-use form factor. Compared to our USB 3.0 thumb drive solution, and even the Intel DC S3500 2.5″ SATA SSD, the Innodisk SATADOM-ML 3ME3 V2 256GB was faster.
The Innodisk SATADOM-ML 3ME3 V2 256GB we reviewed in this article is one of the largest capacity SATADOMs on the market. It also has 8 Pin power delivery to ease integration. Performance was above smaller capacities while in some cases rivaling larger 2.5″ SSDs. For some OSes, such as Windows Server 2012 R2 and Windows Server 2016 you want a larger boot device, and this may be the prime candidate. In terms of pricing and availability, we found these at UnixSurplus for $179 new. That is only around $40 more for double the capacity of the 128GB model. The price per GB is higher than many SSDs, however saving a drive bay is often worth hundreds of dollars in a server which is why SATADOMs are so popular. For many applications, the smaller capacity drives are going to be the right fit. However, for some OSes and storage capacity requirements, you will want a 256GB SATADOM instead.