Unmanned Systems Technology 038 l Skyeton Raybird-3 l Data storage l Sea-Kit X-Class USV l USVs insight l Spectronik PEM fuel cells l Blue White Robotics UVIO l Antennas l AUVSI Xponential Virtual 2021 report

40 Focus | Data storage In larger UAVs, where a data storage system could be a VPX card with hundreds of terabytes of storage, system designers are currently looking at 1 Pbyte of storage. Network Attached Storage NAS devices allow other computers in the network to access files, creating files with their own defined formats and editing and moving files as desired. Data recorders serve a very similar function in many cases, especially when recording Ethernet traffic. However, the data recorder is passive, in that the data source doesn’t need to know that the data is being recorded, and the control computer only has to send simple commands to the recorder. Many data recorders also implement NAS functionality, allowing users to read from the recorded data files. A typical application of this type is in processing systems that need to store data to an NAS during operation. The data can be stored for post-mission analysis, but can also be accessed by users and decision-makers while the operation is still ongoing. One advantage of NAS over other methods of transferring data between deployed platforms and base stations is the ability for all the networked computer systems to access the same centralised data storage system. Sensor data can be sent to the NAS during a mission for post-mission analysis. The sensor data typically goes directly to the mission system, but for post-mission analysis the data is stored on the NAS. Operating the drives inside the NAS as a RAID array will use up only a small amount of the drive’s capacity. For the most basic RAID architecture, this is a very small overhead for the identifiers related to the array. For other RAID formats that might use multiple drives to store the same information, significant amounts of storage are lost for duplication or other redundancy and data recovery mechanisms. NAS devices are specified by the Ethernet connections they support. In most cases, that will be only one type, for example GbE 1000Base-T or 10GbE, but it can also be a mixture. Having homogenous network connections simplifies the cabling requirements but there may be a need to have a mixture of Ethernet connections, for example with GbE ports that are used for streaming sensor data to the NAS, although a 10GbE port is desirable for fast access by the back-end processor using that data. Similarly, 10GbE can be used for fast copying of data to or from the NAS at the start and end of a mission. In contrast to direct attached drives, NAS read/write bandwidth is often limited by network performance. Using large packet sizes can improve network performance, which would also improve NAS bandwidths, but it can reduce reliability as the loss of one large packet is worse than the loss of a small one, and error correction becomes a bigger issue. Controlling the packet size is easier for a data recorder application where a data- streaming device is sending the data than it is with NAS. But NAS applications can modify the performance as well, as lots of separate small file accesses will reduce the bandwidth. NAS drives are not necessarily large. One design for small unmanned aerial and ground systems has four GbE ports for NAS applications, with a removeable storage module offering up to 40 Tbytes of industrial-grade MLC storage or up to 20 Tbytes of military-grade SLC storage, supporting RAID modes 0 and 1. June/July 2021 | Unmanned Systems Technology Network Attached Storage units don’t have to be large (Courtesy of Galleon Embedded) One advantage of NAS is the ability for all the networked computer systems to access the same centralised data storage system