Linux 5.1 Arrives

https://www.zdnet.com/article/linux-5-1-arrives/

by CrankyBear • 7 years ago

107 43 7 years ago

zdnet.com

kawsper• 7 years ago

Whats the current status of the situation between the ZFS-on-Linux project and Linux 5.1+?

burtonator• 7 years ago

How is ZFS in general vs btrfs?

ZFS is basically killed by Oracle right?

Wowfunhappy2• 7 years ago

ZFS is basically killed by Oracle right?

Uh, no? OpenZFS is being actively developed and maintained, albeit not by Oracle.

ComputerGuru• 7 years ago

btrfs is a dumpster truck on fire and everyone serious about their data has switched to ZoL or is holding out in hopes that bcachefs won't be a similar clusterfsck (which shouldn't be too hard to do).

analogkid2• 7 years ago

No, OpenZFS is alive and thriving and we use it in production on many Centos systems.

btrfs is a awful. We used it for a brief time on a production system with vanilla mirrored drives. Absolutely horrible. I will never use btrfs for anything ever again. I've been running unix systems for 30 years; even the darkest days of UFS was not that bad.

2Ccltvcm• 7 years ago

ZFS on Linux is where the majority of ZFS innovation is these days. Btrfs should be permanently deleted except for a sole copy in a museum somewhere as an example of a historical mistake negatively affecting millions of people.

nisa3• 7 years ago

Broad general statements are always difficult but FWIW:

- btrfs is fine if you want checksumming for your external HDD with some backup stuff that is mostly sequential i/o.

- For everything else - especially anything that goes beyond a single disk use ZFS. btrfs RAID1 is not really raid1 but rather oddness of pid decides which drive to read from, raid5,6 had serious issues a while back - the write hole problem still exists for btrfs. ZFS stripe, mirror, raidz are well understood and work flawless afaik. btrfs also does strange things when replacing disks, like going read-only when one disk fails - at least it used to be that way.

- performance is a mixed bag but broadly speaking for anything that is not sequential io on an empty disk btrfs is slower than other filesystems[1], for ZFS it depends can be slower or faster than ext4 depending on a lot of settings...

- ZFS tooling is far superior to btrfs - I've used both a lot and you won't go back to btrfs tooling once you've used ZFS.

- btrfs snapshots degrade performance with rising snapshot count. ZFS works fine.

- ZFS has native encryption with zfs send / recv support in the upcoming 0.8.0. So you can do encrypted differential backups this way.

- btrfs quota was for a long time broken and error-prone, not sure what the current status is but it never worked correctly for me.

- ZFS lacks cp --reflink and linux pagecache integration as well as sendfile() on Linux and the ZFS ARC is independed of the pagecache - that has some consequences for e.g. mmap().

- ZVOLs are ZFS only you can create block devices as ZFS datasets i.e. zfs create -V 10G rpool/xfs && mkfs.xfs /dev/zvol/rpool/xfs && mount /mnt /dev/zvol/rpool/xfs can be useful for ceph, running docker on xfs volumes in container

- btrfs works fine inside containers so you can run Docker in LXD/LXC - ZFS is not there yet - overlay2 support is also missing.

- no io-scheduling via cgroups for ZFS afaik because the Linux queue subsystem is not used...

- Last but not least: ZFS has ZIL & L2ARC. ZIL is huge for spinning disks because sync() writes are first written to an ssd storage and later async and sequential to the hdd. TL;DL: apt update and databases are fast even on spinning disks. L2ARC is an SSD-Cache but it's not so effective in my experience (low hitrate for typical hosting stuff)

- Personally I will avoid using btrfs if I can.

1: https://www.phoronix.com/scan.php?page=article&item=freebsd-... it's a little bit apples/oranges because ZFS Freebsd != Linux ZFS but IMHO it shows that the architecture/design is sound.

zlynx• 7 years ago

ZFS is OK I suppose, but it isn't native. So you have to jump through hoops to use it, just like Nvidia binary graphics drivers.

BTRFS works well. I've used it for a NAS since 2012. It started with two mirrored 2 TB WD RED drives. Since then it's gone through an expansion to 6 drives in RAID 10 and two drive failures and replacements. Pretty decent performance and never a serious problem.

I've also used it on two laptops with SSD. It had some weird edge cases there using Docker with a lot of snapshots and running out of space for metadata. Unlike some people, I found it pretty straight-forward to recover by adding more space using either a USB drive or reusing my swap partition.

BTRFS snapshots are easy to do and great for backups and Docker image layers.

I felt the need to write this because your comment got three or four anti-BTRFS responses, and BTRFS has always been good to me.

nisa3• 7 years ago

current git works fine - 5.1 compat fixes just landed - https://github.com/zfsonlinux/zfs/commits/master

josteink• 7 years ago

I don’t think the kernel people have reverted their ZoL-hostile changes, if that’s what you’re asking about.

That said: ZoL works with Linux 5.0, but AFAIU that’s due to ZoL falling back to less optimal code. I know it works because I run both on my laptop.

jolmg4• 7 years ago

The first of these is Linux now supports persistent memory as RAM. Sure, non-volatile memory (NVM) isn't as fast as good old RAM, but on newer systems it gives you the option of expanding your memory.

That sounds like swap. What's the difference?

greggyb2• 7 years ago

SSD on DIMM.

24gttghh• 7 years ago

So, a RAM Drive?

https://en.wikipedia.org/wiki/RAM_drive

vbezhenar• 7 years ago

I think that this article explains it somewhat: https://lwn.net/Articles/777212/

Basically there's Intel Optane DIMM which costs less than DRAM and offers good enough performance, so you can use Optane with DRAM as a cache and those patches provide proper Linux support for that scheme.

dvfjsdhgfv• 7 years ago

Basically there's Intel Optane DIMM

These chips are extraordinary, when the prices finally go down to a reasonable level it will be another revolution in both persistent (speed) and volatile (size) memory.

jolmg4• 7 years ago

Isn't swap basically expanded memory while using DRAM as cache? It seems like this could be just a different way of operating that cache.

I wonder if this new feature would be used with swapon/swapoff or if it would need a different interface.

haberman• 7 years ago

Swap has to get paged into real RAM when there is a page fault (presumably evicting something else). I'm guessing that this is actually mapping the NVM directly into the process, so individual loads and stores write directly to the device instead of actual RAM.

jolmg4• 7 years ago

That seems like an implementation detail done for the performance of prioritizing the use of the faster device. If you need something that's in storage/swap, chances are you're going to need it repeatedly and so it's a performance boost to "swap" that with whatever is being used least in RAM.

From a functional point of view, it's still really just expanding your memory with a persistent storage device.

I'm guessing that this is actually mapping the NVM directly into the process, so individual loads and stores write directly to the device instead of actual RAM.

If this were the only difference, then it would be just swap without its main optimization and for no noticeable benefit. I doubt this is all there is to it.

andrius4669• 7 years ago

https://kernelnewbies.org/LinuxChanges more detailed changelog

thaumaturgy• 7 years ago

Oh goodie, I get a new kernel version to compile repeatedly for the next few days.

If any of you are successfully rocking Linux on an LG Gram (especially the 17Z990), and you have decent ACPI support, I'd loooooooove to see your kernel config file. Please.

silversconfused2• 7 years ago

Posting your current config would allow others to see if their own is relevantly different. Sorry I can't help though, I'll be building this for an arm chromebook, not a pc, so my configs will be nothing helpful.

wyld_one• 7 years ago

Hm storage as RAM. Sounds like what IBM AS/400 was doing like 30 years ago for mini-frame machines.

senectus1• 7 years ago

Those things were rock solid as well...

yellowapple• 7 years ago

A lot of the current server trends are basically reinventing wheels that were already spinning on mainframes multiple decades ago.

kjeetgill• 7 years ago

One of the coolest new features was just on HN: Efficient IO with io_uring, the new async I/O interface in Linux 5.1 https://news.ycombinator.com/item?id=19843464

Personally I'm most excited for "Safe signal delivery in presence of PID reuse". I think the kernel/syscall boundary has so many cracks when it comes to race-conditions. It really shows how much has changed with respect to concurrency.

zelly• 7 years ago

It also has the Spectre/Meltdown mitigations, which happen to significantly decrease performance.

Linux 5.1 Arrives

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