RaidZ1 and Raidz2 VDevs?

[Derf]

Hi folks,

First post. I'm happy to be here!

Background:
Currently I have two laptops that backup automatically to an Apple Time Capsule (wifi router + HD) - BACKUP #1

I have 4.5+ TB of data (movies, pictures, music, home video, work files, etc) on external USB/Firewire drives and I want a central repository for all of this for easy access and as a secondary backup. -MISC STORAGE

I also have an AppleTV 2 that I would like to serve the movies/music to from this repository without having to have a laptop running.
There are also 3 iPhones that I would like to be able to stream music from the repository.

Backup #1 is really only for the common use items (current work files, a few pics, etc), and doesn't cover all the LARGE data, like the movies, family pictures, home videos, etc). It is really only to serve for recovery of a failed laptop drive. MISC STORAGE is where the bulk of the large data resides; scattered across various drives. It is the PRIMARY repository for the bulk of my data and I'd like a unified backup solution, that is also capable of serving the content more easily than finding/plugging in external drives.


Lead up:
These requirements have led me to become interested in setting up a new NAS box and I want to get into using FreeNAS for my needs.
The box has 4 blank 2TB SATA drives (NL-Enterprise) and 6 1TB SATA drives (consumer).

I'd like to arrange two VDev's (as per the recommendation not to have more than 9 drives in a VDev).
One VDev would be the four 2TB drives, and one VDev would be the six 1TB drives.
I'd like to make the four 2TB drives RaidZ1 (total file size ~6TB), and the six 1TB drives RaidZ2 (~4TB)

Question:
1) Is this possible? - to have a RaidZ1 Vdev and a RaidZ2 Vdev? Is there a better solution to be offered?
2) If not possible, since most of my data is static (once its on there mostly it is only being read off, not re-written) is RaidZ1 sufficient for both VDev's? Is that a bad idea?

 

[titan_rw]

Yes, you can mix vdev types in a zpool. Best practices is not to, and to also use the same number of drives in each vdev.

With the drives you have though, I wouldn't be too worried about mixing vdev types.

The only 'caution', is having a single parity (raidz1) vdev of 'large' drives. If you have to resilver (replace) one of the 2tb drives, then you're relying on the remaining 3 drives to operate at 100%, with no read errors, or silent data corruption. If there's any errors from the remaining 3 drives while resilvering, there's no way zfs can fix it. It will be able to tell you which file(s) were affected though. Of course there's also the chance two drives will develop issues within the time it takes to get replacements.

Depending on your comfort level, and the types of data your storing, this may be an acceptable tradeoff for the extra storage space of a z1 vdev.

For the 6 1tb drives, I'd definitely do raidz2.

Whatever system you use, go with 8GB of ram, or more. 16 would be better.

Always remember, raid of any kind is not a substitute for backup.

 

[CAlbertson]

....
Question:
1) Is this possible? - to have a RaidZ1 Vdev and a RaidZ2 Vdev? Is there a better solution to be offered?
2) If not possible, since most of my data is static (once its on there mostly it is only being read off, not re-written) is RaidZ1 sufficient for both VDev's? Is that a bad idea?

Are you planning to keep the data on the Raid and also us the same Raid as a backup? No. That is not a good idea. You can't have the data and it's backup copy on the same NAS.

But yes you can have multiple raids that use different configurations all on the same box. You can build a three-disk raidz1 and then later build much larger raidz2. At that point I'd copy the data from the raidz1 and then pull the drive out of the system.

For backup you'd like to have the data disconnected and inside a fire safe in some other building. Yu need to have at least one copy "un plugged". The most common reason for loosing data in a raid setup in going to be NOT a failed disk but a lighten strike on the power line, a house fire, theft of the equipment. You might say "that will never happen" but everyone who has ever lost data said that.

It turns out the drives that are in the same box tend to fail together. Maybe it is the power supply inthe box that fails and take them all down. I just suffered a simulations drive failure, the box's drive controller chip failed and wrote junk to the drives. Lucky I had backups in the safe. but they were a week old.

Now I keep the primary copy of the data, an online, connoted hourly backup (Apple's Time Machine) and I rotate and of line set of drives.


So. About the raidz1 system I said I'd take apart. Put those drive to use as a backup to be kept in a safe. So my method is, when yu run out of storage on the NAS, add a MUCH bigger raid, at LEAST 2x the current size, copy the data then remove the old raid. recycle the drives into a "portable" backup set

Bottom line is NEVER depend on the redundancy of raid to substitute for a proper backup. If you do you will eventually loose data.

But on the other hand, if the data is only a bunch of ripped videos. Who cares? So keep the videos in a raid1 system with no backup. But you need a better backup for things you can't replace.

 

[Derf]

Yes, you can mix vdev types in a zpool. Best practices is not to, and to also use the same number of drives in each vdev.

Thank you, this does answer my question, although I'm not sure why it is best practice to do this - it certainly doesn't make for a flexible system.

For the 6 1tb drives, I'd definitely do raidz2.

OK, that sounds like the textbook answer for anyone operating that many disks in a VDev.

Whatever system you use, go with 8GB of ram, or more. 16 would be better.

Thanks for the suggestion, I've read the manual, I'll have 16GB RAM.

Always remember, raid of any kind is not a substitute for backup.

I realize this, however I have no current backup plan at all. I have a version of JBOD - scattered across several USB disks - storing my data. The RAID array is a primary backup in case a USB disk fails - or the USB disk is a backup in case the RAID fails.

Are you planning to keep the data on the Raid and also us[e] the same Raid as a backup? No. That is not a good idea. You can't have the data and it's backup copy on the same NAS.

You can look at it as the data is on the RAID, and the backup is on the scattering of USB disks. While you may argue that it is not a good (enough) idea, but it is a much better idea than not having a backup solution at all (as is my current situation).

But yes you can have multiple raids that use different configurations all on the same box. You can build a three-disk raidz1 and then later build much larger raidz2. At that point I'd copy the data from the raidz1 and then pull the drive out of the system.

Thank you for answering my question, but I have absolutely no idea why you are suggesting this: building a three-disk RAIDZ1 (of 2TB drives = 4TB total, not even enough to duplicate my current data needs as stated above), and then later building a larger RAIDZ2, copy the data from the RAIDZ1, and then pull the RAIDZ1. In fact, I was under the impression that once a VDev is added to a Zpool, you cannot remove it from the pool, which would mean that I would not be able to just "pull" the RAIDZ1 drives. No?

For backup you'd like to have the data disconnected and inside a fire safe in some other building. Yu need to have at least one copy "un plugged". The most common reason for loosing data in a raid setup in going to be NOT a failed disk but a lighten strike on the power line, a house fire, theft of the equipment. You might say "that will never happen" but everyone who has ever lost data said that.

It turns out the drives that are in the same box tend to fail together. Maybe it is the power supply inthe box that fails and take them all down. I just suffered a simulations drive failure, the box's drive controller chip failed and wrote junk to the drives. Lucky I had backups in the safe. but they were a week old.

Now I keep the primary copy of the data, an online, connoted hourly backup (Apple's Time Machine) and I rotate and of line set of drives.


So. About the raidz1 system I said I'd take apart. Put those drive to use as a backup to be kept in a safe. So my method is, when yu run out of storage on the NAS, add a MUCH bigger raid, at LEAST 2x the current size, copy the data then remove the old raid. recycle the drives into a "portable" backup set

Bottom line is NEVER depend on the redundancy of raid to substitute for a proper backup. If you do you will eventually loose data.

Now you're just lecturing, and while you are probably trying to be supportive to a noob, it is quite condescending to assume I don't know this already. My question was simply can I have different RAIDZ configurations in the same ZPool, and you are telling me that I need to have text-book 3-2-1 backup methods.

But on the other hand, if the data is only a bunch of ripped videos. Who cares? So keep the videos in a raid1 system with no backup. But you need a better backup for things you can't replace.

A salient point, and noted. Thanks.

 

[titan_rw]

I think he was meaning build a separate pool, and copy all data to it, then remove the old drives. I have no idea where the 3 drive z1 suggestion came from.

If you have enough external usb drives to keep a second copy of the data you feel needs backing up, then I'd call that a backup. Keep in mind usb drives on freenas is generally frowned upon, so I'd probably use other machines to connect the usb drives to when you need to update your usb copies. A manual backup on usb drives is better than no backup at all.

You're correct, you can't remove vdevs from a pool. (true enough for this conversation). You have to backup, destory / recreate the pool, and restore.

As to flexibility in expanding zpools, I think it comes from the fact that zfs was primarily designed with large datacenter style servers in mind. As opposed to us mere mortals at home that are using it thanks to freenas and freebsd supporting it.

And 'best practices' is just that, 'best'. There's also 'ok' practices. And of course 'not recommended' practices as well. I have previously used a zpool of 3 1tb drives in z1, and 2 1.5tb drives in mirror. All of them were external esata drives as well. And using port multipliers in the external enclosures. That would be one of those 'not recommended' setups: External drives, port multipliers, and two single parity vdevs. For the time I used it though, it worked ok. At the time, it was simply a backup pool.

Personally, being that you have some form of backup (ie second copy of data), I'd probably do the z1 and z2 setup. Setup scheduled scrubs, and email alerting for smart issues.