Should I choose one big SSD or Multi-small HDD
I would like to collect data by using five D455. If I choose one big SSD or one big HDD, will my data lose frames. If I follow the above configuration, will d455 collect data normally? Would it be a better choice if I installed multiple HDDs on the industrial computer?
Thank you for your patience!
-
I would recommend SSD because of its improved access speed compared to older HDD technologies such as SATA. If you will be recording camera data in the bag file format then a large drive is recommended because individual bag files are typically gigabytes in size if the recording duration is longer than a few minutes. If all five cameras are recording data then this will multiply the amount of storage space required.
If the possibility of losing data if a single large drive fails is a concern then you could investigate professional drive backup systems such as NAS so that a backup copy of the main drive is stored on another drive. With NAS, you can easily add additional drives as your storage needs grow over time. Intel has an introductory article about NAS technology in the link below.
In regard to how the choice of drive would affect performance: whilst a fast drive such as SSD is important to help to avoid bottlenecks during recording, in a multiple-camera system where the cameras are all attached to the same computer and are active simultaneously, I would also recommend a computer with an i7 CPU.
-
If I install a 3T SSD on the IPC, when five cameras store data to this SSD at the same time, will this SSD read/write aspect cause a bottleneck, after all, five cameras data transfer speed and volume are very large. If a single SSD solution is feasible, then how fast should I buy an SSD that transfers?
-
If you need to use a single PC and you will be using camera settings that will result in high data volumes, and you will be connecting the cameras to a USB hub, that could result in there being insufficient bandwidth available on a single hub to meet the needs of all the cameras. The subject of hub bandwidth is discussed in the section of Intel's multiple camera white-paper document linked to below, including scenarios for how much bandwidth may be consumed by certain stream modes and quantities of camera.
Assuming that a hub has on average 5000 Mbps (megabits per second) available bandwidth to share among all the devices attached to it, you could instead consider attaching more than one USB hub to the computer and spreading the cameras across them (e.g 3 cameras on one hub and 2 on another hub). Ideally the hubs should be the same manufacturer / model to ensure that they all have the same type of USB controller for consistent performance.
If you have the option of choosing a PC instead of using an existing one then you could look at models suitable for industrial use that have multiple USB ports so that the cameras can be connected directly to the computer instead of using a hub. An example of an industrial-suitable PC with multiple USB 3 ports that is small and powerful is Intel's own NUC 8 VR mini-PC.
https://www.intel.co.uk/content/www/uk/en/products/docs/boards-kits/nuc/mini-pcs/nuc-8-vr.html
Attaching a camera directly to a computer's USB port instead of a hub should be more efficient because each USB port on the computer should have its own dedicated USB controller, whereas a hub may have a USB controller handle a couple of ports.
I'm not aware of simultaneous multiple camera read-write resulting in a drive access bottleneck with a single drive. Multiple cameras would be more likely to place a burden on the resources of other aspects of the computer such as the CPU and graphics GPU.
The RealSense SDK can be configured to offload processing work from the CPU to the GPU for certain types of processing such as depth to color alignment, pointclouds and color conversion. The SDK can also be configured to take advantage of multiple CPU cores if they are available, at the cost of a slightly higher CPU percentage usage.
I am not an expert on drives and so do not have a particular recommendation. My understanding is that a good modern SSD drive may have read speeds in the range of of 550 mbps and write speeds of 525 mbps, whilst an NVME drive will offer significantly faster speeds. The guide in the link below may be useful for research.
https://www.gamingpcbuilder.com/ssd-ranking-the-fastest-solid-state-drives/
-
Thank you for your assistance! However, My IPC has got five USB 3.1 interfaces，so I don‘t consider the hub. At present, I am going to use the CPU model R7 5700G, 16g memory and 750W power supply. The only one confusion is that I'm not sure whether to use a single hard disk (storing the data of five D455 at the same time) or multiple hard disks (each hard disk only stores the data of one D455).
Which one should I choose to make my five cameras work properly? Besides， I didn't get some information about the selection of Hard Disk from the WHITEPAPERS.
Sincerely thank you for your help.
-
Creating a single application that can save each camera to an individual drive path would be slightly more complicated than saving all cameras to the same path. I would speculate that you could set up each camera on its own individual pipeline and streaming configuration, specify the exact serial number of the camera device to use for a particular pipeline, and set the record path with cfg.enable_record_to_file(<path name>)
The link below has an example of a program script in the Python language for defining multiple camera pipelines with unique configurations and accessing the camera by their specific serial number to ensure that you know exactly which drive a particular camera will record to.
https://github.com/IntelRealSense/librealsense/issues/1735#issuecomment-390840337
You could also use the above technique to record to a single large drive, setting the path to a separate folder for each particular camera.
You have a large PSU that could handle 5 separate drives. So if you are going to be frequently recording large volumes of high resolution camera data from 5 cameras, it may be best to give each camera its own individual drive to access. This is because an SSD drive will have a limited number of writes during its lifetime (Terabytes Written, or TBW), as described in the link below, so writing 5 cameras to one drive could shorten the drive lifespan.
https://www.enterprisestorageforum.com/hardware/ssd-lifespan-how-long-will-your-ssd-work/
Please sign in to leave a comment.
Comments
6 comments