The hard disk of the CN2 server in Hong Kong is the physical carrier of data storage and the core bottleneck of system performance. The current mainstream hard disks are divided into three major technical routes: mechanical hard disk (HDD), solid-state hard disk (SSD) and NVMe protocol hard disk, each carrying different business scenarios. HDD relies on rotating disks and mechanical seek of magnetic heads. The capacity of a single disk can reach more than 20TB, and the cost per GB is less than US$0.02, but the random read and write latency is as high as 5-15ms, and the IOPS is only 100-200, which is suitable for low-frequency access scenarios such as log archiving and video storage. SSD is based on NAND flash memory chips, has no mechanical structure, and has a random read and write of 100,000-1 million IOPS, with a latency of less than 0.1ms, which is suitable for high IO load businesses such as databases and virtualization. NVMe hard disks are directly connected to the CPU through the PCIe bus, support multi-queue parallel processing (such as 64K queue depth), and the bandwidth can reach 14GB/s under the PCIe 5.0 interface, and the latency is reduced to microseconds, making it the first choice for AI training and real-time trading systems.
The hard disk interface protocol directly affects the performance ceiling. The SAS interface (compatible with SATA) is preferred in enterprise-level scenarios. Its dual-port redundant design supports hot plugging, MTBF exceeds 2 million hours, and 12Gb/s bandwidth meets key business needs. However, due to the lack of redundant paths, the SATA interface is only recommended for non-core storage pools; NVMe completely releases the performance potential of solid-state drives by eliminating protocol stack overhead.
Tiered management strategy
In terms of the performance layer, NVMe SSDs carry high-frequency transaction data, such as database index files, and need to be configured with enterprise-level solid-state drives with ≥3 DWPD (daily full disk write times) to ensure durability.
In the capacity layer, high-density SATA HDDs store cold data, and large-capacity disks of more than 18TB are combined with power consumption control of ≤8W/disk to reduce costs.
In terms of the redundancy layer, SAS hard drives form RAID arrays, RAID 5/6 balances performance and fault tolerance, and RAID 10 guarantees high-concurrency business.
What are the chain hazards of disk space exhaustion? When the system disk is full, the service startup script cannot write temporary files, causing the Apache/Nginx process to crash; when the application disk is full, the database transaction log writing will be interrupted, triggering the risk of data loss; when the backup disk is full, the incremental backup chain will be broken, and the disaster recovery capability will be reduced to zero. The out of memory (OOM) killer may be activated to forcibly terminate the process that occupies the most memory. At this time, even if the file is deleted, if the process does not release the handle (check through `lsof | grep deleted`), the space cannot be recovered, and the service needs to be restarted or the process needs to be terminated.
Active defense system
1. Real-time monitoring: Deploy tools such as Zabbix to track disk usage, inode consumption (`df -i`) and SMART health indicators, and immediately issue an alarm when the water level exceeds 80%
2. Intelligent cleaning: Log rotation (logrotate) compresses historical files, and the database automatically archives old data; the scheduled script cleans the /tmp directory (`find /tmp -type f -mtime +7 -delete`)
3. Elastic expansion: Use soft links to migrate high-frequency write directories (such as /var/log) to independent partitions. When the original disk space is insufficient, mount a new disk and redirect:
mkdir /newdisk/logs
mv /var/log/ /newdisk/logs
ln -s /newdisk/logs /var/log4. Storage optimization: Enable transparent compression (such as ZFS gzip), configure deduplication strategy, and reduce space usage by 30%-70%
Data security requires redundant architecture support. Key business systems use RAID 10 to resist double disk failures, and use LVM to achieve online expansion of volume groups. Full backup (weekly) and incremental backup (daily) are stored separately, and synchronized to remote computer rooms or cloud storage using rsync. Regular recovery drills verify the effectiveness of backups to avoid the fatal trap of "successful backup but unable to restore".
Hong Kong CN2 server hard disk management is essentially a triangular game of performance, cost, and reliability. Use NVMe to accelerate hot data, rely on SAS arrays to ensure availability, use large-capacity HDDs to reduce TCO, and then resolve space crises through automated monitoring and flexible architecture - the four-layer defense system allows the data engine to continue to operate at high speed in the business torrent.
