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No thanks. I use raidz2. With mirror vdevs if you lose the wrong 2 drives you lose everything. I can lose any 2 drives and be totally fine. The probability of

No thanks. I use raidz2. With mirror vdevs if you lose the wrong 2 drives you lose everything. I can lose any 2 drives and be totally fine. The probability of losing the wrong 2 drives at once is small, sure. But I would rather just not care about that probability. And I don't lose half my capacity, which for a home user (I don't have an unlimited budget!) matters a whole lot more than having the absolute best iops.

segfaultbuserr 6y ago
The original article already included a reply to this question. > But wait, why would I want to trade guaranteed two disk failure in RAIDZ2 with only 85.7% survival of two disk failure in a pool of mirrors? Because of the drastically shorter time to resilver, and drastically lower load placed on the pool while doing so. The only disk more heavily loaded than usual during a mirror vdev resilvering is the other disk in the vdev – which might sound bad, but remember that it’s no more heavily loaded than it would’ve been as a RAIDZ member. Each block resilvered on a RAIDZ vdev requires a block to be read from each surviving RAIDZ member; each block written to a resilvering mirror only requires one block to be read from a surviving vdev member. For a six-disk RAIDZ1 vs a six disk pool of mirrors, that’s five times the extra I/O demands required of the surviving disks. I think it's perfectly okay to disagree. But any comment must contain a counterargument to be useful, for example, one could've argued that load is not an issue in a small array and so on, and I may happily accept the other side of the argument. However, I respectfully criticize that your comment doesn't include any counterargument, it's not useful, please read the article more carefully next time.
- somehnguy 6y ago
  It’s not a question, it’s a statement and my opinion on the matter. I respectfully criticize that your comment isn’t helpful at all nor a counter argument and is therefore useless as well. Please read my comment more carefully next time.
67868018 6y ago
You don’t lose everything, only the files that were on that vdev. I’ve been through this. It’s not fun, though, and your pool is irreversibly damaged but your data is not all lost

segfaultbuserr 6y ago

The original article already included a reply to this question. > But wait, why would I want to trade guaranteed two disk failure in RAIDZ2 with only 85.7% survival of two disk failure in a pool of mirrors? Because of the drastically shorter time to resilver, and drastically lower load placed on the pool while doing so. The only disk more heavily loaded than usual during a mirror vdev resilvering is the other disk in the vdev – which might sound bad, but remember that it’s no more heavily loaded than it would’ve been as a RAIDZ member. Each block resilvered on a RAIDZ vdev requires a block to be read from each surviving RAIDZ member; each block written to a resilvering mirror only requires one block to be read from a surviving vdev member. For a six-disk RAIDZ1 vs a six disk pool of mirrors, that’s five times the extra I/O demands required of the surviving disks. I think it's perfectly okay to disagree. But any comment must contain a counterargument to be useful, for example, one could've argued that load is not an issue in a small array and so on, and I may happily accept the other side of the argument. However, I respectfully criticize that your comment doesn't include any counterargument, it's not useful, please read the article more carefully next time.

somehnguy 6y ago
It’s not a question, it’s a statement and my opinion on the matter. I respectfully criticize that your comment isn’t helpful at all nor a counter argument and is therefore useless as well. Please read my comment more carefully next time.

67868018 6y ago

You don’t lose everything, only the files that were on that vdev. I’ve been through this. It’s not fun, though, and your pool is irreversibly damaged but your data is not all lost