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Comment by BoingBoomTschak | Hacker News Reader

What a wonderful surprise! The nearest thing seem to be modern (v5) XFS + dm-integrity, I'll have to see a comparison once it's stable enough.

A thing ZFS suffers from is fragmentation (no way to defragment in-place nor preallocate so stuff like bittorrent doesn't play well with it), which it justifies with its CoW design, wonder if/how it mitigates the problem.

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>modern (v5) XFS

Is still silly, for the same reasons Hans Reiser documented in an article about Reiser4's design.

e.g. its b-tree stores directories and small files in the same level of the tree, which makes directory operations bloated, while also hurting cache lines.

Fortunately, neither ZFS, Hammer2 or GEFS suffer from this.

You can, to some degree, do an online defrag with zfs rewrite -P now although it is not the primary intent. The displayed fragementation may not go down or may even increase, but all the files will go through the allocation policy. zfs fragmentation display is a little misleading, it measures free space fragmentation.

If we're looking at 'future' filesystems, is fragmentation really an issue in an SSD world? Not that there isn't a lot of spinning rust (and will be for quite a while), I don't think it's unreasonable to assume "most block storage is going to be SSD in the future" when allocating resources to priorities.

The day I can furnish my NAS in SSDs for roughly the same price as HDDs probably won't come before any current filesystem is obsoleted for some reason or another, methinks.

Probably true. My bad.

Fragmentation in ZFS wastes a lot of space. So it doesnt matter if it's SSD or not.

You're right...I didn't think that through.

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