Over more than a decade, Kent ITS designed and operated a complete virtualisation and backup platform built entirely on refurbished enterprise hardware, open‑source hypervisors, and a fully CLI‑driven tape backup system. The platform supported business‑critical workloads including email, file storage, identity services, and application servers. Despite strict budget constraints, limited storage, and ageing hardware, the system delivered continuous uptime, reliable recovery, and long‑term retention using a combination of XCP‑ng, Xen Orchestra, and dual‑drive LTO tape rotation.

The Challenge

The environment evolved over many years and faced several real‑world constraints:

Vendor limitations — VMware’s free edition restricted backups, API access, and live migration.
Ageing hardware — initial hosts were DL380 G5 and DL360 G6 servers sourced from the secondary market.
Limited storage — the QNAP NAS provided only modest iSCSI/NFS capacity, restricting VDI retention depth.
No budget for commercial backup tools — all backup operations had to be built using Linux CLI tools.
Tape capacity limits — LTO4 and LTO5 tapes could not hold 30 days of VDI snapshots as the environment grew.
Need for air‑gapped protection — backups had to be physically removable and independent of cloud services.
Zero‑downtime requirements — hypervisor upgrades and hardware refreshes had to be performed live.

The challenge was to maintain a reliable, recoverable virtualisation platform with long‑term retention while working entirely within these constraints.

The Solution

1. Migration from VMware to XenServer/XCP‑ng

To escape VMware’s limitations, the platform was migrated to XenServer 7 and later upgraded in‑place to XCP‑ng while workloads remained online. This provided:

Live migration
Open storage formats
Flexible upgrade paths
Full CLI access
No licensing restrictions

A three‑node DL360 G6 cluster was built, backed by a QNAP NAS providing iSCSI and NFS storage for VM disks and backups.

2. Hardware Evolution to DL360 G9

As workloads increased, two G6 nodes were replaced with DL360 G9 servers. The mixed‑generation pool remained stable thanks to XCP‑ng’s broad hardware support, improving:

CPU performance
RAM capacity
Power efficiency
Overall reliability

3. Fully CLI‑Driven Tape Backup Architecture

A dedicated DL360 G6 backup server was equipped with two tape drives:

LTO4 on /dev/st0
LTO5 on /dev/st1

The backup system was built entirely using:

tar
mt
cron
Xen Orchestra streaming
NFS/iSCSI storage

Key Engineering Features

a. Streaming VDI backups directly to tape

Xen Orchestra streamed full and incremental VDI chains at ~110 MB/s directly into tar, avoiding:

filesystem overhead
millions of tiny files
tape shoe‑shining
local disk requirements

b. Compressing file‑level data locally

Zimbra and Samba data were compressed into a single backup.tar.gz to maximise tape efficiency and simplify restores.

c. Splitting workloads across two tape drives

To maximise throughput:

LTO4 handled the compressed archive
LTO5 handled VDI streams and metadata

This allowed both drives to run at full speed simultaneously.

d. Automated tape rotation

Cron scripts:

set tape block sizes
generated archives
streamed data to tape
ejected tapes automatically

The onsite person simply removed the tape and took it off‑site.

4. Retention Strategy

The system maintained:

Daily full backups on tape
Incremental VDI chains in Xen Orchestra
14‑day hypervisor snapshots
Months of VDI history across rotated tapes

Retention depth was adjusted as VDI chains grew and QNAP storage became constrained, ensuring tapes remained within capacity while still providing long‑term recovery.

Outcome

Despite limited hardware and no commercial backup tools, the platform delivered:

Zero data‑loss incidents
Reliable recovery from tape when required
Continuous uptime during hypervisor migrations
Long‑term retention without cloud dependency
A fully auditable, vendor‑independent backup format
Maximum value extracted from refurbished hardware