Chapter 165: Redundancy and Breakpoints

By three in the morning, the screen’s glow had turned harsh. Lin Chen blinked his dry eyes and pulled his gaze back to the document. The cursor blinked steadily in the blank space, like a heartbeat.

Local Caching and Consistency Verification Plan Under Network and Power Outage Conditions. Beneath the title, he had listed three core points. No theoretical derivations, only engineering implementation.

First: each edge node would carry a 32 GB industrial-grade TF card using the ext4 journaling file system. At the instant of power loss, the kernel would automatically flush buffered data to disk; if a write failed, the block would be marked dirty and prioritized for verification at the next boot.

Second: every packet header would carry a CRC32 checksum and a monotonically increasing sequence number. Once the network came back, the script would compare sequence numbers, discard duplicate packets, and fill in missing segments.

Third: at the hardware level, a 4700 μF electrolytic capacitor would be connected in parallel to the Raspberry Pi’s GPIO power line, providing roughly fifteen seconds of buffered power after an outage—enough time for the file system to finish committing data to disk.

He typed the last line. The knuckles of his fingers gave a faint crack. Then the calf muscle in his left leg suddenly seized, like a taut string plucked hard without warning. He sucked in a breath, bent down at once, grabbed his ankle with both hands, and pulled his toes back toward his body. A blunt pain climbed along the nerves with the stretch and took more than ten seconds to ease. He held the position until his breathing steadied again.

The thermos at the corner of the desk had gone cold. He unscrewed it and swallowed two mouthfuls of cold water. A slight spasm tightened in his stomach, but he ignored it. He saved the document, renamed it Defense_Appendix_Network-and-Power-Outage_Contingency_V1.pdf, and dragged it onto the USB drive.

Outside the window, the dawn had begun to pale into gray-white. Somewhere in the dormitory building came the first sound of running water from someone washing up. Lin Chen shut down the computer and unplugged the power. When he stood, his left foot still had no sensation, and he had to let his right leg take the weight. He went to the sink and splashed cold water over his face. In the mirror, the man looking back had dark circles under his eyes and stubble coming in along his jaw, but his pupils were steady.

He knew the people in the conference room would not care how the code had been written. They only cared whether the thing would fall apart once it was dropped into a workshop.

At 7:40, he pushed open the conference room door exactly on time.

Three people sat on the far side of the long table. Professor Zhou was on the left, the review form spread open in front of him. On the right sat two men in dark jackets. The older one had gray at his temples, thick knuckles, and black engine-oil grime embedded under his nails that no washing could fully remove. The younger one wore black-rimmed glasses and was flipping through the project application with his head down. The room carried a faint smell of tea and old paper.

“Sit,” Professor Zhou said, lifting his chin. “This is Engineer Liu from the Provincial Heavy Industry Group’s equipment department, and this is Director Chen from the informatization center. They’ve read your project. Today they only care about implementation.”

Lin Chen pulled out a chair and sat down, plugging the USB drive into the port. The PPT appeared on the screen—no animation, only architecture diagrams and parameter tables. He began in an even voice.

“The system uses an edge-computing architecture. The data acquisition layer handles sensor signal conditioning, the processing layer runs Python cleaning scripts, and the transmission layer reports to the cloud over MQTT. The core design principles are: usable on weak networks, storable offline, resumable after power-up.”

Engineer Liu did not look at the screen. His eyes dropped to Lin Chen’s foot, rested there for two seconds, then moved away.

“You’ve run data in workshop conditions. You know the interference is heavy. So I’ll ask the most practical question.” He leaned forward, hands clasped on the table. “If there’s a trip on site, or the fiber gets cut, and both power and network are down for more than two hours, how does your system make sure the data isn’t lost, duplicated, or corrupted? Don’t tell me about cloud synchronization. The workshop doesn’t have that many ideal conditions.”

Once the question landed, the room went quiet for several seconds. Professor Zhou lifted his teacup and said nothing.

Lin Chen opened the appendix slide. The plan diagram he had finished the night before appeared on the screen.

“Engineer Liu, I designed for the worst-case workshop scenario. First, local storage does not depend on the network. Each node has a built-in TF card and uses a journaling file system. At the instant of power loss, the capacitor provides fifteen seconds of buffer power and the system forces a disk flush. Once the data is committed, a verification code is written with it.”

He switched to the next slide and brought up the data-flow diagram.

“Second, protection against duplication and dirty data relies on sequence numbers and CRC32. After the network is restored, the script pulls the local logs and compares them with the cloud side. Any mismatched sequence numbers are automatically retransmitted; duplicates are discarded directly.

“Third, if the outage lasts longer than the capacitor buffer, the file system marks itself as abnormal. On the next boot, the script runs a consistency check first, repairs dirty blocks, and only then resumes acquisition. The whole process requires no manual intervention and does not depend on the cloud.”

He paused, then added, “The added cost of this scheme is mainly the TF card and the capacitor. Hardware cost per node increases by fifteen yuan. But under extreme conditions, it can keep data integrity at no less than 99.2 percent.”

Engineer Liu stared at the architecture diagram on the screen. His fingers tapped the tabletop twice. He did not ask about the technical details. Instead he asked, “Fifteen yuan. If I deploy two hundred nodes, that’s three thousand. Whether the factory approves that money depends on whether you can reduce downtime. Can your script warn of motor bearing wear in advance?”

“Yes.” Lin Chen pulled up another chart. “The vibration signal goes through a Fourier transform to extract characteristic frequencies. The fault frequency of the bearing outer race is fixed. The script sets a threshold. If it exceeds that threshold three times in a row, the local buzzer alarms and a text message is pushed to the duty network administrator. There’s no need to wait for cloud analysis. The edge side responds directly.”

Director Chen pushed up his glasses and finally spoke. “What about maintenance? The workers in the plant don’t know code. What happens if the script crashes?”

“The script is packaged as a service and starts automatically at boot. On failure, it restarts automatically. The network administrator only needs to check the log file size once a week. If it exceeds 500 MB, that means cached data is piling up and a manual sync is needed once. The operating instructions are attached at the end of the application packet. There are only three steps: insert the USB drive, click Sync, remove the USB drive.”

Lin Chen answered quickly, without hesitation.

Engineer Liu leaned back in his chair. A very shallow curve tugged at the corner of his mouth. “Crude, maybe. But it can be implemented. The workshop doesn’t need fancy flourishes. It needs something that can take a beating.” He turned to Professor Zhou. “Professor Zhou, this student understands engineering. The plan can move into the second-phase pilot.”

Professor Zhou nodded and signed his name on the review form. “Lin Chen, the pilot starts next month. Go back and prepare the deployment package first. Engineer Liu’s side will send the coordination checklist.”

The meeting ended at 8:40. Lin Chen packed up his computer and stood to thank them. By the time he stepped out of the conference room, the sun in the corridor had already slanted across the terrazzo floor. He made his way downstairs slowly with one hand on the wall. The numbness in his left foot had begun spreading toward his knee, and with every step the muscles in his right leg were compensating harder for it. At the stair landing he stopped, took a deep breath, and waited for the dull soreness to pass.

His phone vibrated in his pocket. He took it out. Two messages lit the screen.

The first was a bank text:

Your savings card ending in 7742 has received 24,000.00 yuan. Balance: 24,035.30 yuan.

The numbers flickered into place. Lin Chen did not pause. He turned off the screen and kept walking.

The second was a WeChat message from Old Zhao:

The factory is putting the phase-two line online next week. The environment is worse than Workshop One—more dust, higher temperature. Can your board handle it? If yes, bring two sets over for testing. Wednesday afternoon.

Lin Chen stopped beneath the plane trees outside the teaching building. The autumn wind rolled fallen leaves over the ground and brushed them against his shoes. He looked down at his left foot. The shoelaces were tied tight, but the fabric around the ankle had already deformed slightly.

He ran the numbers once. Components for two boards would cost eight hundred. Travel and lodging for the factory trip would be another two hundred. Materials for dustproofing and waterproofing modifications would cost a hundred and fifty. The balance was enough to cover it—but he had only four days.

The script would need its cooling logic adjusted for a high-dust environment. The casing would have to be prototyped again. The sealing strip would need to be replaced with an industrial-grade one.

He took out his phone and typed a reply with his thumb:

Yes. I’ll be there Wednesday afternoon.

Send.

He put the phone away, turned, and headed toward the electronics market outside the campus. His gait was still uneven, but the rhythm of it was steady. Wind moved through the street, carrying the distant pounding of pile drivers from a construction site.

The road ahead was still long, but at least he had mapped the holes in it. The next step was to shove the board into the mud and see whether it could still breathe.