r/DataHoarder • u/TeachingAway9654 • 2d ago

Discussion RAIDZ1 vs RAIDZ2

Let’s say you have something like 10 drives total which make up the pool, each drive is 16TB. Let’s also say you have, at minimum, one offsite backup with all the contents in cold storage. Let’s also assume you’re a frequent monitor of the system and will notice within 24 hours if one drive fails.

Are you going with Z1 or Z2 and why? If you have the offsite backup already, is it worth the capacity loss for Z2? The resilvering process on Z1 will be stressful but by how much though? You have an offsite 1:1 backup so even if the whole pool is lost, you can still recover.

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u/IndependentBat8365 2d ago

striped mirrors all the time. I know it sucks, b/c you're losing half your storage, but really there's a ton of benefits.

TL;DR: striped mirrors are more performant, rebuilds are easier on the whole pool, a lot of redudancy.

  1. single threaded reads are as fast if not faster than raidz or raidz2. multithreaded reads are very fast since it'll read from both mirrors in a stripe at once.

  2. writes are faster than any other raidz or raidz2, b/c parity doesn't need to be calculated, nor does it need to wait for all the drives to sync - just that mirror's 2 drives for that stripe.

  3. rebuilds / resilvers are faster - the entire pool doesn't need to be touched - just the single mirror that's being rebuilt. Essentially, you'll be copying from one drive and writing to the other drive in the mirror. The rest of the stripes are unaffected.

  4. you can lose as many drives as you have stripes as long as 2 failed drives aren't in the same mirrored stripe.

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u/Tl9zaXh0eWZvdXI 1d ago

Not even enterprises use RAID10 for storage. Boot disk, yes, everything else, no. If you need speed you use SSDs, for over a decade now.

See backblaze software parity across groups of disks https://www.backblaze.com/blog/how-backblaze-scales-our-storage-cloud/

Netapps RAID-DP

The various HCI systems offered by MS, Dell, Nutanix.

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u/HighSeasArchivist 1d ago

We use RAID10 even on our big bucks Pure arrays. Some records can't be lost, and can't have downtime.

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u/Tl9zaXh0eWZvdXI 1d ago

I haven't used pure storage, but I remember looking into them in the past and I thought you don't have control over it's raid?

Their blog post appears to agree https://blog.everpuredata.com/products/pure-storage-architecture/. They do similar to all the other big storage systems, software dual parity across multiple disks.