Basic principles and functions of disk media scans


Storage systems periodically read disks for a scan to detect potential faults.
The scanned objects include member disks of a RAID group, hot spare disks, and free disks, ensuring that all disks in use are in good conditions.
By default, the scan period is 30 days. In a scan period, all disks will be scanned. If a system has over 100 disks, you are advised to select a scan period of 60 days (modifiable) to reduce the impact on system performance.

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VRRP implementation principle and basic functions of an S series switch
S series switches (S1700 excluded) support the VRRP function. Virtual Router Redundancy Protocol (VRRP) integrates multiple routing devices into a virtual routing device, and the IP address of the virtual routing device is used as the default gateway address to communicate with external networks. When the gateway is faulty, VRRP can select a new gateway to transmit data traffic, ensuring network reliability. The working process of VRRP is as follows: 1. The VRRP group selects a new master based on the priorities of devices. The master sends gratuitous ARP packets to notify the connected network devices or hosts of the virtual MAC address of the VRRP group, and forwards packets to the virtual IP address. 2. The master periodically sends VRRP Advertisement packets to all backup devices in the VRRP group to advertise its configurations (such as the priority) and operating status. 3. If the master is faulty, VRRP elects a new master from the VRRP group based on priorities. 4. After a VRRP master/backup switchover, the new master sends gratuitous ARP packets carrying the virtual MAC address and virtual IP address of the virtual router to update the MAC address entry on the connected host or device. The user traffic is then switched to the new master. 5. If the original master recovers and is the IP address owner (its priority is 255), it immediately switches to the Master state. If the original device has a priority less than 255, it will switch to the Backup state first, and recover its priority to the previously configured priority before the faulty occurs. 6. If a backup router's priority is higher than the master router's priority, VRRP determines whether to re-elect a new master, depending on the backup router's working mode (preemption or non-preemption).

Basic disk concept
A basic disk contains primary partitions and extended partitions containing logical drivers that are used by Windows 2000 and Windows NT operating systems. Basic disks may also include volumes created by using Windows NT 4.0 or early versions, striped volumes, mirrored volumes, or RAID-5 volumes (also called striped volume with a parity check). As long as the file formats are compatible, basic disks can be accessed by Microsoft MS-DOS, Microsoft Windows 95, Microsoft Windows 98, or Windows NT operating system.

Full disk scanning for hard disks of the USG6000 series
Disks may be bumped during delivery, which may cause disk failures. Before usage, you can perform full disk scanning to repair the disks. Full disk scanning takes 2 to 3 hours. Note: Hard disk self-check interrupts hard disk services. Exercise caution when you perform full disk scanning. 1. Install the hard disk to the device. 2. In the system view, run the disk offline command to enable the hard disk to go offline. 3. In the diagnose view, run the disk self-test enable command to perform full disk scanning. 4. In the diagnose view, run the display disk self-test command to view the result of disk self-check. Progress: displays the progress. For example, in 2/46, 46 indicates that the operation may take 46 minutes, and 2 indicates that 2 minutes have elapsed. The actual time taken shall no longer than 46 minutes. Otherwise, the disk is faulty. ErrorType: Selftest complete without error: indicates that the hard disk is not faulty. Send command failed!: indicates that you shall run the self-check command again. Other: indicates that the hard disk is faulty, and you need to replace it or contact professionals for analysis. DiskSN: indicates the SN of the current hard disk. The self-check result corresponds to the SN.

Steps for scanning VM hard disks
You can scan a hard disk as follows: 1. On the taskbar of the VM OS, select Start and enter compmgmt.msc in Search programs and files to go to the Computer Management window. 2. In the navigation tree on the left, expand Storage. 3. Right-click Disk Management and choose Rescan Disks.

Principle for the MCA board to implement optical spectrum scanning
The MON port of a monitored board outputs weak optical power through an optical splitter. After being connected to the MON port of the board, the MCA board performs appropriate compensation so that the MON port output power of the monitored board is close to the actual optical power output by the OUT port of the monitored board.

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