In Praise of ZFS on Linux's ZED 'ZFS Event Daemon' • Hacker News Board

Re: In Praise of ZFS on Linux's ZED 'ZFS Event Daemon'

#71

Post by tw04 » Mon, Jul 20, 2020, 3:37 PM UTC

briffle wrote: post #56

m0zg wrote: post #29

Earlier quoted context omitted.

> ZFS is fine, but it is overkill for most home applications Yeah, not having silent data corruption is "overkill", sure. /s Why not use ZFS? It takes 15 seconds to install, and its CLI is fairly intuitive. Works fine. Costs $0. Why not, even for "home" applications? I could see how it could be unsuitable for "entreprise" applications where there are strict performance requirements etc, but for home, I wish I could u…

or install BTRFS and be able to detect bitrot as well, but also be able to grow your storage by adding more disks. (even different sizes)

RAID-Z expansion is being worked on: https://github.com/openzfs/zfs/pull/8853

Last I checked BTRFS RAID5/6 was a dumpster fire and unusable in production. Have they actually open sourced the ability to fix bitrot detection with mdraid? If not, it's kind of irrelevant.

So... once again down votes without response - BTRFS raid still isn't recommended and the file healing isn't compatible with MDRAID I assume and you just don't like the fact I pointed it out? The "I'm downvoting because you pointed out a flaw in my logic" @HN is disappointing.

Re: In Praise of ZFS on Linux's ZED 'ZFS Event Daemon'

#72

Post by notabee » Mon, Jul 20, 2020, 4:04 PM UTC

StavrosK wrote: post #33

acd wrote: post #11

Insightful article. Zfs is the best file system. Ability to know that you do not have silent file corruption. Running without raid controllers. Feature to take snapshots super fast without waiting and that take little extra space. You can use Cache SSD with ZFS for read acceleration of physical disk. Transparent file compression. Good command line interface. Now you can take good actions with ZED for example sending…

I have a home NAS that has an SSD on it for the OS and four HDDs in RAIDZ. Does anyone know if/how I can use a small part/partition of the SSD for the cache? I don't need an entire SSD's worth of cache, and I'd rather not have to buy an extra one.

Most of the time you don't need the extra SSD cache. If you do use one for the ZIL (writes), it will only help synchronous writes, it should be redundant if possible, and it should be extremely low latency like Intel Optane. L2ARC (reads) on an SSD is not as good as just adding more RAM.

Re: In Praise of ZFS on Linux's ZED 'ZFS Event Daemon'

#73

Post by theamk » Mon, Jul 20, 2020, 4:05 PM UTC

louwrentius wrote: post #28

acd wrote: post #11

Insightful article. Zfs is the best file system. Ability to know that you do not have silent file corruption. Running without raid controllers. Feature to take snapshots super fast without waiting and that take little extra space. You can use Cache SSD with ZFS for read acceleration of physical disk. Transparent file compression. Good command line interface. Now you can take good actions with ZED for example sending…

I would advice people to think about what they need. ZFS is fine, but it is overkill for most home applications and it has a pitfall related to extensibility. https://louwrentius.com/what-home-nas-builders-should-unders... https://louwrentius.com/the-hidden-cost-of-using-zfs-for-you... So it really depends on your needs. Statements as "ZFS is the best filesystem" are so meaningless. P.S. SSD caching often has no tang…

Silent data corruption is a real thing, I have a few thousands files for the evidence.

If you are building a home NAS from quality rackmounted server parts, then maybe you are fine. But this was not an option for me, as I did not have dedicated server space and needed something quiet. And once you have to start with to mess with desktop cases full of hard drives, it is very easy to get corrupted data.

I run ZFS on my home NAS. Yes, it (probably) eats too much RAM, and it (probably) not the fastest thing, but at least my data is intact. I had to piece together my photo collection from multiple backups, it was not fun at all.

Re: In Praise of ZFS on Linux's ZED 'ZFS Event Daemon'

#74

Post by e40 » Mon, Jul 20, 2020, 4:06 PM UTC

drewg123 wrote: post #45

louwrentius wrote: post #28

Earlier quoted context omitted.

I would advice people to think about what they need. ZFS is fine, but it is overkill for most home applications and it has a pitfall related to extensibility. https://louwrentius.com/what-home-nas-builders-should-unders... https://louwrentius.com/the-hidden-cost-of-using-zfs-for-you... So it really depends on your needs. Statements as "ZFS is the best filesystem" are so meaningless. P.S. SSD caching often has no tang…

The thing I never see mentioned when the pros and cons of ZFS are discussed is that ZFS is not zero-copy for things like sendfile. This is one reason why we (Netflix) use UFS for serving content rather than ZFS. This is because ZFS is cached by the ARC, not the normal page cache. ARC is weird, and operates in 8K blocks (like sparc page size), rather than 4K pages. Zero-copy things like sendfile depend on referencing…

UFS on what OS?

Re: In Praise of ZFS on Linux's ZED 'ZFS Event Daemon'

#75

Post by theamk » Mon, Jul 20, 2020, 4:08 PM UTC

louwrentius wrote: post #54

mapgrep wrote: post #39

Earlier quoted context omitted.

Disagree that data integrity is “overkill for most home applications.”

Tell that to all those Mac, Linux and Windows users on their daily desktops and laptops. Almost none of them have even ECC memory.

Memory has much fewer “moving parts” than disk. You cannot get bad “memory cable”, and (AFAIK) there are no cases when overloaded power supply caused memory errors,

Re: In Praise of ZFS on Linux's ZED 'ZFS Event Daemon'

#76

Post by infogulch » Mon, Jul 20, 2020, 4:12 PM UTC

ddorian43 wrote: post #63

seqizz wrote: post #53

Earlier quoted context omitted.

We've been running for about a year now and had zero problems with it. (~20TB total, few single instances, serving as S3 backend to Restic - handmade HA - backup service)

What do you mean with "handmade HA" ?

Perhaps a high-availability system they made themselves?

Re: In Praise of ZFS on Linux's ZED 'ZFS Event Daemon'

#77

Post by anthk » Mon, Jul 20, 2020, 4:24 PM UTC

e40 wrote: post #74

drewg123 wrote: post #45

Earlier quoted context omitted.

The thing I never see mentioned when the pros and cons of ZFS are discussed is that ZFS is not zero-copy for things like sendfile. This is one reason why we (Netflix) use UFS for serving content rather than ZFS. This is because ZFS is cached by the ARC, not the normal page cache. ARC is weird, and operates in 8K blocks (like sparc page size), rather than 4K pages. Zero-copy things like sendfile depend on referencing…

UFS on what OS?

FreeBSD.

Re: In Praise of ZFS on Linux's ZED 'ZFS Event Daemon'

#78

Post by [deleted] » Mon, Jul 20, 2020, 4:28 PM UTC

mapgrep wrote: post #40

viraptor wrote: post #17

Earlier quoted context omitted.

Btrfs has pretty much the same features listed above minus the cache drive handling. (You can still get the cache drive behaviour over bcache device) The raid has different modes, so you'll have to decide if what's available is enough for you. You can check the status of each feature here: https://btrfs.wiki.kernel.org/index.php/Status

It’s also still considered experimental and according to kernel.org wiki “under heavy development.” ZFS was released for production use 14 years ago.

[deleted]

Re: In Praise of ZFS on Linux's ZED 'ZFS Event Daemon'

#79

Post by giantrobot » Mon, Jul 20, 2020, 4:30 PM UTC

e40 wrote: post #74

drewg123 wrote: post #45

Earlier quoted context omitted.

The thing I never see mentioned when the pros and cons of ZFS are discussed is that ZFS is not zero-copy for things like sendfile. This is one reason why we (Netflix) use UFS for serving content rather than ZFS. This is because ZFS is cached by the ARC, not the normal page cache. ARC is weird, and operates in 8K blocks (like sparc page size), rather than 4K pages. Zero-copy things like sendfile depend on referencing…

UFS on what OS?

NetFlix is a heavy FreeBSD shop, so I'd assume FreeBSD.

Re: In Praise of ZFS on Linux's ZED 'ZFS Event Daemon'

#80

Post by trasz » Mon, Jul 20, 2020, 4:34 PM UTC

StavrosK wrote: post #51

magnetic wrote: post #50

Earlier quoted context omitted.

What do you mean? I've done this not so long ago on my pool. https://unix.stackexchange.com/questions/530968/adding-disks...

You can't add disks to a vdev, though, which is what most people with a home NAS (including me) want.

You can add them to RAID0/1 vdevs; you can't add them to RAIDZ vdevs. Which you don't have if you don't run ZFS. You might have RAID5, but then you also have a write hole.