Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

ZFS 2.3 released with ZFS raidz expansion

github.com

Post reply on HN
Print view View original

161–170 of 331 posts

Re: ZFS 2.3 released with ZFS raidz expansion

#161

Post by poisonborz »

bayindirh wrote: post #127
poisonborz wrote: post #59

I just don't get it how the Windows world - by far the largest PC platform per userbase - still doesn't have any answer to ZFS. Microsoft had WinFS and then ReFS but it's on the backburner and while there is active development (Win11 ships some bits time to time) release is nowhere in sight. There are some lone warriors trying the giant task of creating a ZFS compatibility layer with some projects, but they are far f…

> How come that Windows still uses a 32 year old file system? Simple. Because most of the burden is taken by the (enterprise) storage hardware hosting the FS. Snapshots, block level deduplication, object storage technologies, RAID/Resiliency, size changes, you name it. Modern storage appliances are black magic, and you don't need much more features from NTFS. You either transparently access via NAS/SAN or store your…

So private consumers should just pay cloud subscription if they want safer/modern data storage for their PC? (without NAS)

Re: ZFS 2.3 released with ZFS raidz expansion

#162

Post by ryao »

crest wrote: post #141
azalemeth wrote: post #96

Earlier quoted context omitted.

My understanding is that single-disk btrfs is good, but raid is decidedly dodgy; https://btrfs.readthedocs.io/en/latest/btrfs-man5.html#raid5... states that: > The RAID56 feature provides striping and parity over several devices, same as the traditional RAID5/6. > There are some implementation and design deficiencies that make it unreliable for some corner cases and *the feature should not be used in production, only…

One problem with your setup is that ZFS by design can't use a traditional *nix filesystem buffer cache. Instead it has to use its own ARC (adaptive replacement cache) with end-to-end checksumming, transparent compression, and copy-on-write semantics. This can lead to annoying performance problems when the two types of file system caches contest for available memory. There is a back pressure mechanism, but it effectiv…

Traditionally, you have the page cache on top of the FS and the buffer cache below the FS, with the two being unified such that double caching is avoided in traditional UNIX filesystems.

ZFS goes out of its way to avoid the buffer cache, although Linux does not give it the option to fully opt out of it since the block layer will buffer reads done by userland to disks underneath ZFS. That is why ZFS began to purge the buffer cache on every flush 11 years ago:

https://github.com/openzfs/zfs/commit/cecb7487fc8eea3508c3b6...

That is how it still works today:

https://github.com/openzfs/zfs/blob/fe44c5ae27993a8ff53f4cef...

If I recall correctly, the page cache is also still above ZFS when mmap() is used. There was talk about fixing it by having mmap() work out of ARC instead, but I don’t believe it was ever done, so there is technically double caching done there.

Re: ZFS 2.3 released with ZFS raidz expansion

#163

Post by cm2187 »

TiredOfLife wrote: post #22
mustache_kimono wrote: post #9

Earlier quoted context omitted.

> It is possible with windows storage space (remove drive from a pool) and mdadm/lvm (remove disk from a RAID array, remove volume from lvm), which to me are the two major alternatives. Don't know about unraid. Perhaps I am misunderstanding you, but you can offline and remove drives from a ZFS pool. Do you mean WSS and mdadm/lvm will allow an automatic live rebalance and then reconfigure the drive topology?

Storage Spaces doesn't dedicate drive to single purpose. It operates in chunks (256MB i think). So one drive can, at the same time, be part of a mirror and raid-5 and raid-0. This allows fully using drives with various sizes. And choosing to remove drive will cause it to redistribute the chunks to other available drives, without going offline.

And as a user it seems to me to be the most elegant design. The quality of the implementation (parity write performance in particular) is another matter.

Re: ZFS 2.3 released with ZFS raidz expansion

#164

Post by bayindirh »

poisonborz wrote: post #161
bayindirh wrote: post #127

Earlier quoted context omitted.

> How come that Windows still uses a 32 year old file system? Simple. Because most of the burden is taken by the (enterprise) storage hardware hosting the FS. Snapshots, block level deduplication, object storage technologies, RAID/Resiliency, size changes, you name it. Modern storage appliances are black magic, and you don't need much more features from NTFS. You either transparently access via NAS/SAN or store your…

So private consumers should just pay cloud subscription if they want safer/modern data storage for their PC? (without NAS)

I think Microsoft has discontinued Windows 7 backup to force people to buy OneDrive subscriptions. They also forcefully enabled the feature when they first introduced it.

So, I think that your answer for this question is "unfortunately, yes".

Not that I support the situation.

Re: ZFS 2.3 released with ZFS raidz expansion

#165

Post by yjftsjthsd-h »

wil421 wrote: post #77
poisonborz wrote: post #75

Earlier quoted context omitted.

Way better data security, resilience against file rotting. This goes for both HDDs or SSDs. Copy-on-write, snapshots, end to end integrity. Also easier to extend the storage for safety/drive failure (and SSDs corrupt in a more sneaky way) with pools.

How many of us are using single disks on our laptops? I have a NAS and use all of the above but that doesn’t help people with single drive systems. Or help me understand why I would want it on my laptop.

If the single drive in your laptop corrupts data, you won't know. ZFS can't fix corruption without extra copies, but it's still useful to catch the problem and notify the user.

Also snapshots are great regardless.

Re: ZFS 2.3 released with ZFS raidz expansion

#166

Post by chungy »

crote wrote: post #146
chungy wrote: post #51

Earlier quoted context omitted.

I'm not sure that's really a caveat, it just means old data might be in an inoptimal layout. Even with that, you still get the full benefits of raidzN, where up to N disks can completely fail and the pool will remain functional.

I think it's a huge caveat, because it makes upgrades a lot less efficient than you'd expect. For example, home users generally don't want to buy all of their storage up front. They want to add additional disks as the array fills up. Being able to start with a 2-disk raidz1 and later upgrade that to a 3-disk and eventually 4-disk array is amazing. It's a lot less amazing if you end up with a 55% storage efficiency ra…

It still seems pretty minor. If you want extreme optimization, feel free to destroy the pool and create it new, or create it with the ideal layout from the beginning.

Old data still works fine, the same guarantees RAID-Z provides still hold. New data will be written with the new data layout.

Re: ZFS 2.3 released with ZFS raidz expansion

#167

Post by formerly_proven »

ryao wrote: post #147
formerly_proven wrote: post #121

Earlier quoted context omitted.

My understanding is that ZFS does virtual physical translation in the vdev layer, i.e. all block references in ZFS contain a (vdev, vblock) tuple, and the vdev knows how to translate that virtual block offset into actual on-disk block offset(s). This kinda implies that you can't actually remove data vdevs, because in practice you can't rewrite all references. You also can't do offline deduplication without rewriting…

There is a clever trick that is used to make top level removal work. The code will make the vdev readonly. Then it will copy its contents into free space on other vdevs (essentially, the contents will be stored behind the scenes in a file). Finally, it will redirect reads on that vdev into the stored vdev. This indirection allows you to remove the vdev. It is not implemented for raid-z at present though.

Though the vdev itself still exists after doing that? It just happens to be backed by, essentially, a "file" in the pool, instead of the original physical block devices, right?

Re: ZFS 2.3 released with ZFS raidz expansion

#168

Post by brian_cunnie »

azalemeth wrote: post #96
lousken wrote: post #74

Earlier quoted context omitted.

as far as stability goes, btrfs is used by meta, synology and many others, so I wouldn't say it's not stable, but some features are lacking

My understanding is that single-disk btrfs is good, but raid is decidedly dodgy; https://btrfs.readthedocs.io/en/latest/btrfs-man5.html#raid5... states that: > The RAID56 feature provides striping and parity over several devices, same as the traditional RAID5/6. > There are some implementation and design deficiencies that make it unreliable for some corner cases and *the feature should not be used in production, only…

> I have personally been bitten once (about 10 years ago) by btrfs just failing horribly on a single desktop drive.

Me, too. The drive was unrecoverable. I had to reinstall from scratch.

Re: ZFS 2.3 released with ZFS raidz expansion

#169

Post by bmicraft »

crote wrote: post #146
chungy wrote: post #51

Earlier quoted context omitted.

I'm not sure that's really a caveat, it just means old data might be in an inoptimal layout. Even with that, you still get the full benefits of raidzN, where up to N disks can completely fail and the pool will remain functional.

I think it's a huge caveat, because it makes upgrades a lot less efficient than you'd expect. For example, home users generally don't want to buy all of their storage up front. They want to add additional disks as the array fills up. Being able to start with a 2-disk raidz1 and later upgrade that to a 3-disk and eventually 4-disk array is amazing. It's a lot less amazing if you end up with a 55% storage efficiency ra…

Well, when you start a raidz with 2 devices you've already done goofed. Start with a mirror or at least 3 devices.

Also, if you don't wait to upgrade until the disks are at 100% utilization (which you should never do! you're creating massive fragmentation upwards of ~85%) efficiency in the real world will be better.

Re: ZFS 2.3 released with ZFS raidz expansion

#170

Post by BSDobelix »

poisonborz wrote: post #161
bayindirh wrote: post #127

Earlier quoted context omitted.

> How come that Windows still uses a 32 year old file system? Simple. Because most of the burden is taken by the (enterprise) storage hardware hosting the FS. Snapshots, block level deduplication, object storage technologies, RAID/Resiliency, size changes, you name it. Modern storage appliances are black magic, and you don't need much more features from NTFS. You either transparently access via NAS/SAN or store your…

So private consumers should just pay cloud subscription if they want safer/modern data storage for their PC? (without NAS)

If you need Windows, you can use something like restic (checksums and compression) and external drives (more than one, stored in more than one place) to make a backup. Plus "maybe" but not needed ReFS (on your non-Windows partition), which is included in the Workstation/Enterprise editions of Windows.

I trust my own backups much more than any subscription, not essentially from a technical point of view, but from an access point of view (e.g. losing access to your Google account).

EDIT: You have to enable check-summing and/or compression for data on ReFS manually

https://learn.microsoft.com/en-us/windows-server/storage/ref...

Post reply on HN