Change / Upgrade drives / need double check

After studying the options that exist, I came to the same conclusion, ZFS seems like the right thing to do. The downside is that ZFS is not yet very flexible regarding expansion procedures. I read somewhere that this year they plan to release new functionalities about it, it is still in development.

Regarding your plan, you will need to copy the data twice. The first in the first 8TB disk and the second when creating the mirror. Since you have a backup, wouldn't it be easier to delete the current Raid and create the mirror with the two 8TB disks? You would only have to copy the data once from your second server.

Zitat von Zoki

Regarding copying twice: wouldn't ZFS automatically resilver the VDEV, if I add a second disk to a VDEV?

I don't know the exact process, but it is logical to think that ZFS will do it automatically as you say, in any case it will end up being a second copy, the data must be transferred to that disk also in one way or another, at the end of the day you are creating a mirror.

If you have free bays on your second server you could do it another way:

- Create the ZFS pool on the second server and copy the data.

- Export the pool and remove the drives.

- Remove the old HP Gen 8 drives.

- Install the two 8TB drives in HP Gen 8.

- Import the pool.

- Reconfigure services.

Downtime would be tight.

If you are going to use ACL permissions you need this:

acltype = posixacl

xattr = sa

Also look at the sector size of your disks, it can be 512B or 4KB. If memory serves me correctly this is set at the beginning in ZFS as well.

Compression to take into account as well, but personally I prefer to define it in file systems. It depends on the content you may or may not be interested in.

Zitat von chente

The downside is that ZFS is not yet very flexible regarding expansion procedures.

Not true my friend, at least in my opinion. ZFS can easily be expanded by adding another Vdev which can be a single disk.

I believe it's better to add mirrors to a pool, but ZFS will allow any kind of Vdev, a mirror, RAIDZ1, a single disk, etc., to be added to an existing pool.

In the following, the pool is made up of a mirror (RAID1 equivalent), RAIDZ1 (RAID5 equivalent)) and at the bottom is a basic volume (a single disk). I did have to use the force option to add the single disk.

This was done in three separate steps, in the GUI:
Create a mirror, then expand adding RAIDZ1, then expand again adding a basic volume



What ZFS won't do is allow any kind of Pool contraction or a Vdev removal. (For this reason, using a single disk as a Vdev is a real bad idea.)

BTRFS allows for an array to be downsized, as in actually contracting the filesystem size and removing devices, but I've never tested it.

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Zitat von Zoki

Questions:
1. Is ZFS the way to go for my needs?
2. I have a lot of hard links (rsnapshot backups). Does ZFS cope with that?
3. Is the plan feasable in your opinion or does it need modification

1. I think you can do it with one modification.
- If you have the room in the case (or could temporarily cable in two drives laying beside the case) I would add a second pool, using the larger 8TB disks in a mirror.
- Use rsync to recreate the entire structure of the existing ZFS array to the new 8TB mirror.
- You wouldn't have to reconfigure OMV. Just redirect the shared folder (music for example) to the recreated music folder / device on the new array. The stuff layered onto the shared folder, like a samba share, will follow.

Once the rsync job is finished, shared folders are redirected and samba shares are tested. Then the older disks could be removed without consequence. Once done the old disks could be wiped, used as a backup pool, or used in another device.

2. I believe it will. If these hard links exist in the current array, the new array should be fine. ZFS did have issues with overlayfs (used by Dockers) a few years ago, but I believe that was solved in later pool versions.

3. You could give your "single disk to a mirror upgrade" a try. It worked fine for me, but it's a command line operation.

I did the following in a VM:

zpool attach poolname existinghdd blankhdd

zpool attach ZFS1 ata-VBOX_HARDDISK_VB5ee42a80-ac4d8f53 /dev/sdd

(Even if it's a bit risky, an shown above, the device name will work as well. )

The above upgraded a single drive to a mirror as follows:

Zitat von crashtest

Not true my friend, at least in my opinion. ZFS can easily be expanded by adding another Vdev which can be a single disk.

I believe it's better to add mirrors to a pool, but ZFS will allow any kind of Vdev, a mirror, RAIDZ1, a single disk, etc., to be added to an existing pool.

You are right, you can add a vdev to an existing pool. But in my opinion this is not a real expansion, you could call it an expansion perhaps. I consider an expansion to add a disk to a mirror vdev and turn this mirror vdev into a 3 disk Raidz1 vdev. Or add a disc to a 3-disc Raidz1 vdev and convert it to a 4-disc Raidz1 vdev. Currently ZFS cannot do this. This is what I mean when I say that this functionality is in development and is expected to be released this year 2022. Or so I read a long time ago. ZFS is a developing technology. mdadm can do this, if I'm not mistaken. I don't know if BTRFS can do it, but I lost interest in BTRFS when I saw the problems they have with the equivalent of mdadm's Raid5 or ZFS's RaidZ1.

On the other hand, it is not recommended in ZFS to add a Raidz1 vdev to a mirror vdev in the same pool. It is recommended to add vdevs of the same type within each pool. It can be done, but it is not the best option. I could not say the reasons, I also read this a long time ago and I do not remember, I suppose that Google will have the answer, as always. I suspect that the resulting pool will be limited as a whole by the worst characteristics of each individual vdev. It's something that I wouldn't do. In this case I would prefer to make a second pool.

That is why I said at the beginning that ZFS is still a bit rigid in its expandability. In the case of Zoki it will have a mirror in a 4 bay box. You simply won't be able to add a single disk to your existing pool in the future. Your best option will be to add another two disks and create another mirror vdev, which in this case could add to the existing pool and have two mirrors within the pool. Unless the actual expansion method has already been developed and you can turn your mirror into a RaidZ1, then yes, you could add a single disk.

Zitat von crashtest

- If you have the room in the case (or could temporarily cable in two drives laying beside the case) I would add a second pool, using the larger 8TB disks in a mirror.
- Use rsync to recreate the entire structure of the existing ZFS array to the new 8TB mirror.
- You wouldn't have to reconfigure OMV. Just redirect the shared folder (music for example) to the recreated music folder / device on the new array. The stuff layered onto the shared folder, like a samba share, will follow.

Zoki cannot add two ZFS mirrored disks to its current box. In his first post Zoki said he has a box with 4 bays and all 4 are occupied. Zoki's initial plan was to downgrade the existing Raid to free up a bay, add a disk as ZFS vdev, copy data, remove the 3 existing disks, add another disk, and mirror the vdev. Read the first post. That is why I suggested creating the pool on another server, exporting and importing. It seemed like an easier way.

Zitat von chente

Zoki cannot add two ZFS mirrored disks to its current box. In his first post Zoki said he has a box with 4 bays and all 4 are occupied.

If he has two additional SATA ports (or even one) on the motherboard, one or two drives can be cabled to the motherboard, laying or even hanging out of the side of the case. One has to be careful not to bump the drives with power applied but it works fine for temporary use. I've done it before.

The second choice, degrading the array to open up a slot, is possible with the option of upgrading a single disk to a mirror. The command line VM exercise was the first time I tried that. It worked without any issues.

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As far as ZFS expansion is concerned, I suppose it's how you look at it. Upgrading ZFS is a bit more ridge than traditional RAID or LVM, but I believe the benefits are worth it. It's just a matter of opinions. Really, there's no right or wrong.

Zitat von Zoki

Yesterday i got my new SAS 8087 to 4 times sata cables and plugged it into my microserver which is open now and has a stack of drives lying next to it

That's cheating.