Btrfs ENOSPC Rework Lands For Linux 4.8, Boosts Throughput & Lowers Latency

[phoronix]

Phoronix: Btrfs ENOSPC Rework Lands For Linux 4.8, Boosts Throughput & Lowers Latency

The Btrfs "enospc-rework" that's been in development for several months by Facebook's Josef Bacik is landing with the Linux 4.8 kernel...

http://www.phoronix.com/scan.php?page=news_item&px=Btrfs-Linux-4.8-ENOSPC

[thelongdivider]

That's really exciting. I wish it wasn't 2 months out (outside of mainline), but this is what BTRFS needs most based on benchmarks I've seen.

[treba]

I'm also really exited to see benchmarks with this new code.
I've been planning to switch to btrfs for a while now for the snapshot, deduplication and compression features. On my space limited ssd system, deduplication and lto compression should give quite a space advantage for my development folder.
With even more speed, there are less and less reasons to stay with ext4.

[horizonbrave]

sorry for sounding silly but would this feature be "backported" to previous kernels or does it depend on the specific distro choices? Cheers

[DrYak]

On my space limited ssd system, deduplication and lto compression should give quite a space advantage for my development folder.

Depending on how much space constrained you are, btrfs administration get a bit more complicated (rebalances, etc).
Also, if you use huge files that get written a lot (VM, Database), CoW leads to some fragmentation (but marking these exceptions manually as no-CoW is easy)


On the other hand:
- btrfs is a copy-on-write system. It never overwrites, it always writes a new copy of a block and updates pointers. That makes it much gentler to flash memory like your ssd.
- recent kernels allow send/receive for easier rsync like backup
- extending the system to raid-1 on-the-fly will be easier when you buy an extra ssd
- checksumming and scrubing is good.

[thelongdivider]

I'm also really exited to see benchmarks with this new code.
I've been planning to switch to btrfs for a while now for the snapshot, deduplication and compression features. On my space limited ssd system, deduplication and lto compression should give quite a space advantage for my development folder.
With even more speed, there are less and less reasons to stay with ext4.

I've been on BTRFS, using LZO compression, for a while now. The thing I've actually found most useful is subvolumes. Aside from a small efi partition, my entire SSD is one BTRFS filesystem with subvols. The fact that I don't need to have a root filesystem and home and var and etc planned out in advance was the biggest space save for me. Compression helps too. For Dedup, can't bedup be used on any filesystem?

[coder]

For Dedup, can't bedup be used on any filesystem?

I don't know what that is, but it seems to me that dedup either must be implemented in the filesystem or atop a filesystem that has CoW.

You can dedup using hard-links, but if the file is modified via one link, then all others would see the change. That's why CoW is needed (unless the data is read-only).