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I'm currently considering a switch from ext4 to ZFS and am having trouble finding information about whether or not it uses more or less space to store the same amount of data as ext4. My understanding is that it uses checksums for data integrity, which I'm assuming comes at a cost of more physical space used when compared to ext4. Since it seems nobody is talking about this, I wonder if perhaps the compression (which I understand is enabled by default) more than makes up for the space used by the checksums?

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The checksumming and space used by it isn't a real consideration. That's why nobody is discussing it. Why are you under the impression that it would take up more than a negligible amount of space? Did you read something to lead you to believe otherwise?

This is easy enough for you to test on your own with your data, though.

I will say that compression (use lz4, please) is worth using on just about any ZFS dataset.

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  • No, I haven't read anything that would lead me to believe that ZFS uses more space than ext4. I just couldn't find anyone talking about how much space the checksums consumed. I had pretty much come to the same conclusion... the lack of anyone complaining about it must mean that it is a non-issue. But, I also wondered if nobody cared because disk space is so cheap these days. We have dozens of servers with small-ish SSD drives (some as small as 256GB) and I wanted to get a preliminary answer on this before I spent the time to start converting the servers over to ZFS. – Curtis May 17 '18 at 1:04

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