SHR vs Traditional RAID: Why Synology Does It Differently

Updated: 2026-04-29

Last updated March 2026 · 8 min read

If you own a Synology NAS, you've probably seen "SHR" as the recommended storage option. But what exactly is Synology Hybrid RAID, and why should you care? The short answer: SHR solves the biggest pain point of traditional RAID when it comes to mixing different drive sizes.

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The Problem with Traditional RAID and Mixed Drives

In traditional RAID 5 or RAID 6, the usable capacity per drive is limited to the size of the smallest drive in the array. If you have three 8TB drives and one 4TB drive in RAID 5, you get 3 × 4TB = 12TB usable. That means 12TB of your 28TB total raw capacity is simply wasted.

This is by design – striped RAID needs uniform stripe sizes. But for home users who upgrade drives one at a time, this is a significant problem.

How SHR Solves This

SHR takes a layered approach. Instead of treating all drives as one uniform array, it creates multiple RAID volumes across "tiers" of equal capacity. Think of it as stacking multiple RAID arrays on top of each other.

With the same 3×8TB + 1×4TB example, SHR-1 creates a RAID 5 array across the first 4TB of each drive (giving 12TB usable), then a RAID 1 pair across the remaining 4TB of the three 8TB drives (giving another 4TB usable). Total: 20TB usable versus 12TB in traditional RAID 5. That is a massive difference.

SHR-1 vs SHR-2

SHR-1 provides single-disk redundancy (like RAID 5) while SHR-2 provides dual-disk redundancy (like RAID 6). The choice depends on your array size. For 2-4 drives, SHR-1 is typical. For 5+ drives, SHR-2 gives you extra safety during the increasingly long rebuild times of large drives.

When Traditional RAID Beats SHR

SHR is not always the better choice. If all your drives are the same size (and you plan to keep it that way), traditional RAID 5 or 6 gives you identical capacity with simpler management. Traditional RAID is also available on every platform – SHR is Synology-exclusive.

Enterprise environments typically prefer traditional RAID for its predictability, wider tooling support, and platform independence. If you might migrate your drives to a non-Synology system later, traditional RAID is the safer bet.

Migration Path

Synology allows online migration from SHR-1 to SHR-2 (adding another layer of parity protection) and from smaller to larger drives. You can replace drives one at a time, rebuild after each, and gradually increase your pool's capacity. This incremental upgrade path is SHR's biggest practical advantage for home users.