Esdebe Consultancy Ltd

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02/06/2026

My Vdev Size Rules

After years of working with ZFS, I've settled on some guidelines I rarely break. For mirrors, two or three disks is perfect. For RAID-Z2, I aim for 6-10 disks. Going wider creates resilver times and risks that I consider unacceptable. It's about finding that sweet spot between efficiency and safety. These aren't arbitrary numbers - they're based on real-world pain I've seen when people ignore them. Do you follow similar guidelines or have you developed your own rules of thumb?

01/06/2026

The Resilver Risk

This is the part that genuinely concerns me with very wide RAID-Z vdevs. When a drive fails, the rebuild process (called resilvering) can take days on large arrays. All that extra work on the remaining drives creates a dangerous window where another failure could mean data loss. This is why I strongly prefer smaller, multiple vdevs over one giant array. The stress during resilver is no joke. What's your biggest concern when designing storage pools?

31/05/2026

RAID-Z Write Performance

One thing many people don't realize until they test it is that RAID-Z writes are more CPU and resource intensive because of the parity calculations. While mirrors just write the data twice, RAID-Z has to do mathematical work on every write. I find this difference becomes very apparent with I/O-heavy applications. It's not a deal-breaker for many use cases, but it's something you need to understand. Have you benchmarked both approaches? What's been your experience?

31/05/2026

RAID-Z1 vs Z2 vs Z3

Understanding the different RAID-Z levels is crucial. Z1 uses single parity, Z2 uses double parity, and Z3 uses triple. While Z1 might seem tempting for capacity, I strongly believe Z2 should be your minimum in 2024. The resilver times on large drives make single parity too risky. This is one of my unbreakable rules now. Where do you stand on this? Are you still using Z1 or have you moved to Z2 and beyond?

30/05/2026

RAID-Z for Maximum Capacity

If your main goal is cavernous amounts of storage, RAID-Z is where it's at. Instead of mirroring data, it uses mathematical parity that allows the system to reconstruct lost data if a drive fails. This makes it far more efficient than mirrors. I consider it the champion of cost-effective bulk storage. Of course, nothing is free - there are performance considerations. Have you built RAID-Z pools? What's been your experience compared to mirrors?

30/05/2026

Mirror Capacity Trade-off

Let's be honest about mirrors - they're not efficient with space. You essentially pay for double the storage to get redundancy. However, in my experience, when you're running latency-sensitive workloads, that trade-off makes perfect sense. The performance and recovery benefits are significant. I always tell people to choose mirrors when performance is king. How do you balance capacity versus speed in your own storage setups? I'd love to hear your approach!

29/05/2026

The Power of Mirror Vdevs

When performance matters most, mirror vdevs are my go-to choice. Every write goes to all disks simultaneously, making random writes extremely fast. Recovery from a drive failure is also incredibly quick. The trade-off is capacity, but when you're running VMs or databases, that speed is worth it. I personally reach for mirrors whenever responsiveness is critical. Would you choose performance over capacity? Tell me in the comments!

29/05/2026

Vdevs Are Permanent

One of the most important things to understand about ZFS is that your vdev design is permanent. You can expand a pool by adding new vdevs, but you cannot modify or add disks to existing ones without destroying and rebuilding them. This is why your initial architecture matters so much. I always treat it like pouring concrete - once it's set, you're committed. Have you ever had to rebuild a pool because of an early design choice? Drop your thoughts below and let me know how you approach your storage planning!

28/05/2026

Match Architecture to Workload

One size does not fit all in storage design. If you're building a home media server packed with movies and photos, RAID-Z2 gives you the capacity you need. But if you're running virtual machines or need low latency, a pool of mirror vdevs will feel dramatically more responsive. I always start by asking: what will this storage actually be used for? The answer should drive your architecture. What are you currently building? Did you choose mirrors, RAID-Z, or a mix? Share your setups below!

28/05/2026

Why I Avoid RAID-Z1

This is something I feel quite strongly about. RAID-Z1 was acceptable with smaller drives years ago, but with today's multi-terabyte drives, the time it takes to resilver makes it dangerous. The statistical probability of a second failure during that window is too high for my comfort. I now recommend RAID-Z2 as the absolute minimum for any serious storage. This isn't theoretical - it's based on watching too many close calls. What's your minimum protection level these days?

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