Analysis of Backup Software Network Architectures: LAN Base, LAN Free, Server Free, NDMP, and Server‑Less

Backup software offers multiple networking modes that can be flexibly deployed according to the existing environment. Most products support the mature LAN Base and LAN Free modes, which both affect business server performance, whereas Server Free bypasses the business server, eliminating backup impact on production workloads.

To alleviate network pressure, many solutions also provide deduplication and compression, reducing the amount of data transmitted over the backup network.

The core components—backup management server, media server, and backup agents—can be deployed independently or consolidated on a single physical server, depending on data volume, bandwidth, and networking requirements; small environments often benefit from consolidation.

When data volumes are large, high‑throughput media servers are required, sometimes in multiple instances that cooperate to share the load.

Using LAN Base or a multi‑site distributed backup also necessitates dedicated media servers at each branch to minimize inter‑site data transfer.

LAN Base Architecture Analysis

In LAN backup, each protected server runs only a backup client (iDA). The media server (MA) on the opposite side must connect to the backup storage, receiving data from all clients over the LAN and writing it to the backup media.

The backup management server issues control commands via LAN to media servers and clients; clients read data and transmit it over LAN to the media server, which writes it to the backup device.

LAN Free Architecture Analysis

LAN Free includes two variants: SAN‑Media and SAN‑Client. SAN‑Media is widely supported; every protected server runs both a backup client and a media server, allowing data to flow directly to the backup media without traversing the production LAN.

SAN‑Client is currently supported only by Veritas NBU and NetWorker. Similar to Simpana, an agent is installed on the business server; the agent transfers data over a storage SAN to the media server, which then writes it to the backup media.

Compared with SAN‑Media, SAN‑Client imposes less load on business servers but requires the media server to run Linux/Unix, equipped with at least two HBAs (one in Target mode to interact with the agent).

Server Free backup clients only issue data‑flush commands, making their impact on servers negligible.

Server Free Architecture Analysis

Server Free enables zero‑window backup by creating a snapshot of the production disk array; the backup server mounts the snapshot and copies its data, avoiding any performance impact on the production system.

This approach requires tight integration between backup software and primary storage to manage snapshots, with iDA agents on both the production server (to issue flush commands) and the media server (to retrieve and mount snapshots), ensuring data consistency with minimal impact.

NDMP Backup Architecture Analysis

NDMP is a standard network backup protocol; since version 4.0 it supports SAN storage, though most vendors still only implement NAS backup. NDMP offers two networking modes: local 2‑Way and 3‑Way, both classified under Server Free.

In the 2‑Way mode, the Data Management Application (DMA) controls data flow from the NDMP host (primary storage) directly to a tape device, bypassing the LAN. The tape library must be attached to an NDMP‑compatible storage unit, and the backup server discovers and loads the tape via NDMP.

NAS devices act as primary storage; the backup server uses NDMP over LAN to instruct the NAS to start backup, after which the NAS sends data over Fibre Channel to a directly attached tape device. NDMP also creates file‑system snapshots on the primary storage, transfers file and directory metadata to the backup server for indexing and management.

In the 3‑Way mode, data moves from the NDMP host to the backup server, then to the media server, which writes it to tape via LAN. This allows multiple NAS devices to share a tape library, with SCSI or Fibre Channel eliminating distance constraints for remote backup.

Server‑Less Backup Architecture

Server‑Less is currently a theoretical design and not widely adopted in enterprises. It relies on an intelligent SAN switch to execute backup commands issued by the client; the storage device directly writes data to tape using extended SCSI‑3 commands. Because it demands strict SAN storage requirements and has poor compatibility, implementation is challenging.

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