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OpenZFS – add disks to existing RAIDZ

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Re: OpenZFS – add disks to existing RAIDZ

#61

Post by jedberg »

globular-toast wrote: post #58
jedberg wrote: post #30

I wish Apple and Oracle would have just sorted things out and made ZFS the main filesystem for the Mac. Way back in the day when they first designed Time Machine, it was supposed to just be a GUI for ZFS snapshots. How cool would it be if we had a great GUI for ZFS (snapshots, volume management, etc.). I could buy a new external disk, add it to a pool, have seamless storage expansion. It would be great. Ah, what coul…

TrueNAS? You can manage the volumes with a web UI. It has a thing you can enable for SMB shares that let you see the previous versions of files on Windows. Or perhaps I don't understand what you're after.

I'm looking for that kind of featureset for my root filesystem on MacOs. :/

Re: OpenZFS – add disks to existing RAIDZ

#63

Post by phs318u »

jedberg wrote: post #30

I wish Apple and Oracle would have just sorted things out and made ZFS the main filesystem for the Mac. Way back in the day when they first designed Time Machine, it was supposed to just be a GUI for ZFS snapshots. How cool would it be if we had a great GUI for ZFS (snapshots, volume management, etc.). I could buy a new external disk, add it to a pool, have seamless storage expansion. It would be great. Ah, what coul…

I had the same thoughts about Apple and (at the time) Sun, 15 years ago.

https://macoverdrive.blogspot.com/2008/10/using-zfs-to-manag...

Re: OpenZFS – add disks to existing RAIDZ

#64

Post by deadbunny »

edmundsauto wrote: post #57
ErneX wrote: post #49

I’m not an expert whatsoever but what I’ve been doing for my NAS is using mirrored VDEVs. Started with one and later on added a couple more drives for a second mirror. Coincidentally one of the drives of my 1st mirror died few days ago after rebooting the host machine for updates and I replaced it today, it’s been resilvering for a while.

I’ve read this is suboptimal because you are now stressing the drive that has the only copy of your data to rebuild. what are your thoughts?

Mirrored vdevs resilver a lot faster than zX vdevs. Much less chance of the remaining drive dying during a resilver if it takes hours rather than days.

Re: OpenZFS – add disks to existing RAIDZ

#65

Post by allanjude »

crote wrote: post #29

> After the expansion completes, old blocks remain with their old data-to-parity ratio (e.g. 5-wide RAIDZ2, has 3 data to 2 parity), but distributed among the larger set of disks. New blocks will be written with the new data-to-parity ratio (e.g. a 5-wide RAIDZ2 which has been expanded once to 6-wide, has 4 data to 2 parity). Does anyone know why this is the case? When expanding an array which is getting full this wi…

That is not how this will work.

The reason the parity ratio stays the same, is that all of the references to the data are by DVA (Data Virtual Address, effectively the LBA within the RAID-Z vdev).

So the data will occupy the same amount of space and parity as it did before.

All stripes in RAID-Z are dynamic, so if your stripe is 5 wide and your array is 6 wide, the 2nd stripe will start on the last disk and wrap around.

So if your 5x10 TB disks are 90% full, after the expansion they will contain the same 5.4 TB of data and 3.6 TB of parity, and the pool will now be 10 TB bigger.

New writes, will be 4+2 instead, but the old data won't change (they is how this feature is able to work without needing block-pointer rewrite).

See this presentation: https://www.youtube.com/watch?v=yF2KgQGmUic

Re: OpenZFS – add disks to existing RAIDZ

#66

Post by mgerdts »

canvascritic wrote: post #45

this is a really neat addition to raid-z. i recall setting up my zfs pool in the early 2000s and grappling with disk counts because of how rigid expansion was. Good times. this would've made things so much simpler. small nitpick: in the "during expansion" bit, I thought he could have elaborated a touch on restoring the "health of the raidz vdev" part, didn't really follow his reasoning there. but overall, looking for…

I remember in the decade+ before zfs was introduced and in several of the years since then trying to figure out the optimal stripe size for RAID 10 volumes and the optimal stripe size and count for RAID 5 volumes with Solaris Disk Suite, VxVM, Linux md, etc. Fixing bad decisions has typically meant backup twice, test a restore, fixe the volume, and pray one of your backups is good. :)

ZFS has generally been easier to go from zero to working well once you accept that life doesn’t need to be so complicated as legacy md, lvm, and fs layers made it. It also has a pretty big footgun that causes me to carefully read the man page before using “zpool add” or “zpool attach”. Vdev removal is a big help for this.

Re: OpenZFS – add disks to existing RAIDZ

#67

Post by wtallis »

hinkley wrote: post #36

I’m frustrated because this feature was mentioned by Schwartz when it was still in beta. I thought a new era of home computing was about to start. It didn’t, and instead we got The Cloud, which feels like decentralization but is in fact massive centralization (organizational, rather than geographical). Some of us think people should be hosting stuff from home, accessible from their mobile devices. But the first and t…

> which rules out all RAID levels except 0, which is nuts.

RAID 1, you mean? Because that way you still have a complete copy of your data if one drive fails.

BTRFS is excellent for the use case of a wide variety of mismatched drives, because it supports adding and removing drives and rebalancing the array. But for the moment only the RAID 1 modes are really trustworthy. I have a NAS consisting of drives whose advertised capacities in GB are: 1000, 1000, 1920, 2000, 2048, 2050, 3840, 3840, 4000. But it started as a pile of infamously unreliable 3TB hard drives.

Re: OpenZFS – add disks to existing RAIDZ

#68

Post by canvascritic »

mgerdts wrote: post #66
canvascritic wrote: post #45

this is a really neat addition to raid-z. i recall setting up my zfs pool in the early 2000s and grappling with disk counts because of how rigid expansion was. Good times. this would've made things so much simpler. small nitpick: in the "during expansion" bit, I thought he could have elaborated a touch on restoring the "health of the raidz vdev" part, didn't really follow his reasoning there. but overall, looking for…

I remember in the decade+ before zfs was introduced and in several of the years since then trying to figure out the optimal stripe size for RAID 10 volumes and the optimal stripe size and count for RAID 5 volumes with Solaris Disk Suite, VxVM, Linux md, etc. Fixing bad decisions has typically meant backup twice, test a restore, fixe the volume, and pray one of your backups is good. :) ZFS has generally been easier to…

oh, the memories of trying to optimize stripe sizes in the pre-zfs days! i can totally relate to the struggles with solaris disk suite and linux md. the pain of fixing poor decisions and the nail-biting backup processes are all too familiar. zfs really did simplify things in many ways. though i agree, it's always a good idea to tread carefully with commands like `zpool add` and `zpool attach`. glad vdev removal has made that process a bit smoother. it's pretty cool to see how storage management has evolved over the years. cheers for the trip down memory lane. :)

Re: OpenZFS – add disks to existing RAIDZ

#69

Post by katbyte »

crote wrote: post #29

> After the expansion completes, old blocks remain with their old data-to-parity ratio (e.g. 5-wide RAIDZ2, has 3 data to 2 parity), but distributed among the larger set of disks. New blocks will be written with the new data-to-parity ratio (e.g. a 5-wide RAIDZ2 which has been expanded once to 6-wide, has 4 data to 2 parity). Does anyone know why this is the case? When expanding an array which is getting full this wi…

I imagine there would eventually be a way / option to automatically rewrite old blocks. Or at least I would hope so because usually when your adding new disks the array is going to be near full

Re: OpenZFS – add disks to existing RAIDZ

#70

Post by hinkley »

wtallis wrote: post #67
hinkley wrote: post #36

I’m frustrated because this feature was mentioned by Schwartz when it was still in beta. I thought a new era of home computing was about to start. It didn’t, and instead we got The Cloud, which feels like decentralization but is in fact massive centralization (organizational, rather than geographical). Some of us think people should be hosting stuff from home, accessible from their mobile devices. But the first and t…

> which rules out all RAID levels except 0, which is nuts. RAID 1, you mean? Because that way you still have a complete copy of your data if one drive fails. BTRFS is excellent for the use case of a wide variety of mismatched drives, because it supports adding and removing drives and rebalancing the array. But for the moment only the RAID 1 modes are really trustworthy. I have a NAS consisting of drives whose adverti…

Raid 1 does not work with heterogenous disk arrays.
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