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Backup Strategies series · Part 3 of 7 Local Backup Media — HDD, NAS, SAN, Tape and MoreWhich medium for which data volume, RPO and budget External HDD · NAS · SAN · LTO Tape · Tape Library · RDX · Optical |
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Choosing the right medium
The previous part (Backup Methods) covered how data is backed up. Now the question is where to. The answer depends on four criteria: data volume, RPO/RTO, retention period and budget. A NAS is ideal for fast, frequent backups; an LTO tape beats every other medium per GB at 5+ years retention. An external hard disk on the server's USB port works as a quick lane but is not enough as the only backup strategy.
Important: Local media typically cover two of the three copies in the 3-2-1 rule. The third copy belongs outside the building — either by relocating physical media (tape, disk in a vault) or into the cloud. Both are covered in the next parts.
Local backup media compared
| Medium | Capacity | €/TB* | Speed | Lifespan | Air-gap? |
|---|---|---|---|---|---|
| External HDD | up to 24 TB | 15–30 € | USB 3 / Thunderbolt | 3–5 years | yes, when disconnected |
| NAS | up to 1 PB+ | 25–60 € | 1–25 GbE | 5–10 years | no (online) |
| SAN | up to multi-PB | 60–200 € | FC, iSCSI, NVMe-oF | 5–10 years | no (online) |
| LTO-9 tape | 18 TB native / 45 TB compressed | 5–10 € | 400 MB/s native | 30 years | yes, ejected |
| RDX cartridge | 500 GB–5 TB | 40–80 € | SATA / USB 3 | 10 years | yes, ejected |
| Blu-ray / M-Disc | 25–100 GB | 100–200 € | 12x BD-XL ~50 MB/s | 100+ years (M-Disc) | yes, immediately |
* Retail prices April 2026, indicative. Prices keep falling; the relative ranking is stable.
External hard disksCHEAP PORTABLE FRAGILE The simplest backup lane: an external hard disk on the USB port, backup software runs, the disk is unplugged and put in the vault. For environments below 5 TB this is a valid complement — but never the only strategy. USB drives have short lifespans under heavy continuous use, are sensitive to shocks, and a theft compromises all data at once (encryption is mandatory). Useful as a rotating disk set: 5–7 disks on rotation (one per weekday), combined with encrypted storage and off-site relocation. For fixed server environments, a drive caddy with SAS/SATA disks is usually more robust and faster. |
NAS — the workhorse of SMB backupsFAST & FLEXIBLE RAID-INTEGRATED RANSOMWARE-EXPOSED A Network-Attached Storage (NAS) is the standard for short-term backups (daily, weekly): high speed via Ethernet, snapshot capability with ZFS or btrfs, integrated RAID for internal redundancy, often a vendor-specific backup app (Synology Active Backup, QNAP NetBak, Asustor Backup). Important for backup use: A NAS mounted via SMB during the day can be encrypted by ransomware. Counter-measures: dedicated backup-NAS with its own AD account, only connected during the backup window, snapshot protection with immutable retention rules, optionally WORM mode (Write Once Read Many). Sizing: rule of thumb 3–5× the gross source data volume to map a GFS scheme cleanly. For 10 TB of source data, that means 30–50 TB gross, depending on retention. For larger setups, a storage server with more disk slots and 10 GbE is more economical than several small NAS units. |
SAN and DASHIGHEST PERFORMANCE EXPENSIVE & COMPLEX A Storage Area Network (SAN) provides block-level access via Fibre Channel, iSCSI or, more recently, NVMe-over-Fabrics. Usually overkill for backup — the value is in production (databases, VM storage). As a backup target it makes sense if SAN infrastructure already exists and a dedicated volume can be carved out. Direct Attached Storage (DAS) is storage attached directly to the server — via SAS HBA, often with a SAS expander backplane for 12 or more disks. For single backup servers a very good and economical choice with performance benefits over NAS. |
LTO tape and tape libraryCHEAPEST LONG-TERM STORAGE NATURAL AIR-GAP SEQUENTIAL ACCESS Linear Tape Open is the established enterprise tape family. Current generation is LTO-9 with 18 TB native per cartridge (45 TB compressed); the roadmap goes up to LTO-14 with 576 TB per tape. The LTO cartridges are remarkably cheap compared to HDD/SSD — and with 30 years archival lifespan (ISO/IEC 14721) the standard for anything legally retention-bound. Tape library: wherever there are more than a handful of tapes, the jump from a standalone drive to a tape library (also: tape storage system) pays off. A robot moves cartridges between slots automatically; the library can run multiple drives in parallel and is directly addressable by backup software. Mid-range setups start at 8–24 slots; enterprise-class libraries go beyond 1,000 slots (PB range). Air-gap advantage: An ejected LTO cartridge in a vault is physically unreachable for ransomware. In 2026 this is the single most effective defence against encryption attacks — the main reason tape is regaining major importance in mid-sized businesses. |
RDX cartridgesSIMPLE LIKE EXTERNAL HDD AIR-GAP CAPABLE RDX combines the operating logic of a removable disk with the robustness of a tape cartridge: RDX cartridges (500 GB to 5 TB) slide into an internal or external dock and are recognised as a normal disk by the OS. Compared to tape, random access is much faster; compared to USB HDDs, the cartridges are more shock-resistant and longer-archivable (10 years vs. 3–5). For small and mid-sized environments a good compromise between operating comfort, air-gap capability and cost. |
Optical media — Blu-ray, M-Disc, UDONICHE · ARCHIVE USE Blu-ray (BD-R, BD-XL up to 100 GB) and especially M-Disc with 100+ years archival lifespan have their niche in legally compliant long-term archiving of small, immutable data sets (notaries, architects, clinics). Available in our shop under Storage media. For larger environments, LTO tape is superior in virtually every respect. |
Frequently asked questions
Is one large NAS sufficient as the only backup target?
No. A single NAS violates two of the three conditions of the 3-2-1 rule (only one media type, not off-site). On top of that, a permanently online NAS is a preferred ransomware target. Use NAS as the primary backup, but always combined with tape or cloud.
Is tape still relevant — isn't it “old technology”?
Quite the opposite: with ransomware as the biggest threat and retention requirements of 10+ years, LTO tape is more relevant than ever. The roadmap (LTO-10 to LTO-14 specified) guarantees investment safety for at least the next decade. Cloud hyperscalers themselves use tape internally (AWS Glacier, Azure Archive Tier).
Which medium for ~5 TB SMB volume?
Classic recommendation: a 4–8-bay NAS with 20–40 TB gross as the daily/weekly target, plus monthly LTO tapes for off-site copies. Investment ~€5,000–8,000 one-off, covers three of the four typical requirements. Add cloud backup for the external copy.
How long does an LTO cartridge really last?
Vendors specify 30 years guaranteed readability when stored at 25 °C and 50 % RH in a stable environment. Field data confirms this. Important: drives are only backwards-compatible by two generations — an LTO-9 drive reads LTO-7/8 but not LTO-6. Plan migration in good time for long retention.
Consulting on backup media and hardwareLooking for the right NAS, a tape library or RDX cartridges for your backup concept? We size your solution together with you — matched to data volume, RTO/RPO and budget. Phone: +49 (0)7666 / 88499-0 · E-mail: sales@industry-electronics.com |
Related shop categories
| NAS & storage serverStorage NAS Storage SAN Storage server Direct Attached Storage |
Tape, RDX & libraryBand/Cartridge Tape array Tape storage systems RDX cartridges |
Hard disks & SSDHard disks SSD SATA · SSD SAS Drive caddies Drive enclosures |
| Servers & controllersServers · Rack-mount RAID controllers |
Optical & generalStorage media Optical media |
Software & UPSBackup software UPS (all) |
Other parts of this series
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You are here: Part 3 — Local Backup Media |
Last updated: April 2026 · Lieske Elektronik · industry-electronics.com