Why Do Dedicated Line VMs Need NVMe?
In enterprise dedicated line services, virtual machines (VMs) perform critical network functions — route forwarding, traffic proxying, VPN termination, traffic shaping, and more. These workloads have fundamentally different storage performance requirements compared to ordinary web servers or database servers.
NVMe (Non-Volatile Memory Express) is a high-performance interface protocol designed specifically for flash storage, connecting directly to the CPU via the PCIe bus and bypassing traditional SATA/SAS interface bottlenecks. Compared to HDDs (mechanical hard drives) and SATA SSDs, NVMe SSDs deliver orders-of-magnitude improvements in random I/O performance and latency.
Areapac's dedicated line VMs exclusively use NVMe storage rather than traditional HDD, because network workloads have rigid requirements for low-latency I/O. Even routing/proxy workloads that seem to "not need much disk I/O" actually depend on storage I/O for log writing, connection state storage, configuration file reads, and kernel swap space usage. If storage latency is too high, these operations block the CPU, which in turn impacts packet forwarding performance.
IOPS Comparison: HDD vs SATA SSD vs NVMe
IOPS (Input/Output Operations Per Second) is the core metric for measuring a storage device's ability to handle read/write requests. Here's a typical random 4K IOPS comparison across three storage types:
7200 RPM HDD: ~80-120 random read IOPS, ~80-120 random write IOPS. Mechanical hard drives are bottlenecked by physical seek time (typically 4-8ms), an insurmountable physical limitation. SATA SSD: ~40,000-90,000 random read IOPS, ~20,000-70,000 random write IOPS. SATA SSDs eliminate mechanical seek latency but are limited by the SATA interface bandwidth ceiling (~550MB/s) and command queue depth (only 32). NVMe SSD: Up to 500,000-1,000,000+ random read IOPS, 200,000-500,000+ random write IOPS. NVMe unleashes flash storage's full potential through direct PCIe connection and 65,535 queue depth.
Regarding latency, HDD typical random access latency is 4-10ms, SATA SSD about 0.1ms, while NVMe SSD can go as low as 0.02ms (20 microseconds). For proxy servers handling hundreds of thousands of network connections per second, reducing storage latency from milliseconds to microseconds translates to significant system throughput improvements.
RAID Levels and Data Reliability
Even with high-performance NVMe SSDs, a single drive failure can still cause data loss and service disruption. RAID (Redundant Array of Independent Disks) combines multiple drives to provide data redundancy and/or performance improvements.
RAID 0 (Striping): Distributes data evenly across drives for improved speed, but with zero redundancy — any single drive failure destroys all data. Not recommended for production. RAID 1 (Mirroring): Each drive has an identical copy. Read performance doubles, usable capacity halves. Provides the simplest redundancy, suitable for small-scale critical systems. RAID 5 (Striping with Parity): Data and parity distributed across three or more drives, tolerating any single drive failure without data loss. Good balance between capacity efficiency and redundancy. RAID 10 (1+0, Mirror + Stripe): RAID 1 mirroring first, then RAID 0 striping. Delivers both high performance and high redundancy, but requires at least 4 drives with 50% usable capacity. This is the preferred RAID level for high-performance applications.
How Storage Affects Packet Forwarding
Many assume routing and proxying are purely "CPU + NIC" workloads where storage performance is irrelevant. This is a common misconception. In practice, the following scenarios generate significant storage I/O:
Connection tracking table overflow: When the conntrack table exceeds memory capacity, the system relies on swap space. If swap resides on slow HDD, each swap operation introduces milliseconds of latency, directly slowing packet processing. Log writing: Security auditing requires logging all connections. Under high traffic, log write frequency is extremely high — slow storage creates I/O bottlenecks, causing log buffer overflows or process blocking. Temporary files and cache: HTTP proxies cache response content, SSL session tickets write to disk — latency in these operations directly impacts user experience. VM disk I/O scheduling: In virtualized environments, multiple VMs share underlying storage. Insufficient storage performance causes I/O contention that spikes latency across all VMs.
Areapac uses NVMe RAID 10 configurations uniformly across all dedicated line service infrastructure, ensuring every VM receives consistently high-performance storage. Combined with self-operated BGP networks and optimized routing policies, every layer from storage to network is carefully tuned to deliver the best possible dedicated line experience for enterprise clients.