External drive backup

[dtom10]

Hello forum,

I'm just beginning with Freenas and NAS in general. My setup is just for home use and I plan on creating a RAIDZ1 pool out of 4 X 1Tb various drives that I've salvaged from my devices. I've taken apart two of my WD Mybook external drives based on WD Green drives. I have another WD Black drive and one Seagate ES series drive.

Yeah, I know it's not something advisable to do but I plan on addressing this matter in the next couple of months. Changing the drives one by one to something larger and with the same specs.

I have another 3Tb Mybook drive that I plan on using as a backup solution if the pool fails. What I need to know if this is a good practice if I create a vdev out of this external drive and mount it on demand to replicate data onto it. I don't see any provisioning in the web interface for this kind of a task.

I would expect some form of mount/umount kind of option for USB drives but I couldn't find one so I'm asking beforehand if that's the way I can do this or not. A second NAS box is out of the question.

 

[Fraoch]

No, FreeNAS doesn't support external drives - quite on purpose. External USB drives just aren't reliable. Most cannot monitor the health of the hard drive using SMART. If they encounter an error, they may just disconnect and reconnect, then continue writing corrupted data.

Also please be aware of the risks you're taking with RAID-Z1. You have 4 drives - ideal for RAID-Z2.

 

[DrKK]

No, FreeNAS doesn't support external drives - quite on purpose. External USB drives just aren't reliable. Most cannot monitor the health of the hard drive using SMART. If they encounter an error, they may just disconnect and reconnect, then continue writing corrupted data.

Also please be aware of the risks you're taking with RAID-Z1. You have 4 drives - ideal for RAID-Z2.

I really hate this RAID-Z fear-mongering. The guy has only *FOUR* drives, and lower capacity ones at that. He's QUITE fine, generally, with RAIDZ. While four drives is ideal, performance-wise, for RAIDZ-2, I assume this gentleman would rather have the extra space of RAID-Z, and with four smaller drives, I think it's totally fine.

 

[dtom10]

Yeah, my reasoning is to keep a less reliable RAIDZ configuration since I'll be changing the drives anyway and also have a backup. The external drive I plan on always keeping offline and make periodic backups onto it. Can I make a vdev out of it and have ZFS replicate the data from the RAIDZ onto it? Is this possible?

 

[Fraoch]

I don't think so - but what you could do is use a connected client to back up the FreeNAS drive. I'm thinking of Deja-Dup on Linux, for example.

 

[rogerh]

Can one add a single disk as a new zpool/volume on the same FreeNAS machine? (Not, obviously as an extra vdev attached to the existing pool.) This could presumably provide a place to backup data which could be physically (after logically) detached.

 

[Ericloewe]

Can one add a single disk as a new zpool/volume on the same FreeNAS machine? (Not, obviously as an extra vdev attached to the existing pool.) This could presumably provide a place to backup data which could be physically (after logically) detached.

It's possible, but not recommended.

 

[mjws00]

I find the USB is not reliable excuse tiresome. Fact is lynx point broke the FreeBSD USB 3.0 drivers. So the decision was made to pull support by default so people with shiny new Haswell boxes could still boot. That is all. There are many cases where USB is an excellent solution, and also some where it is poor. There are also "great" USB chipsets and devices, and "poor" USB chipsets and devices. They didn't break this on purpose or make a conscious decision to remove external USB drive support because it is "Bad".

This is a significant weakness on the platform. Period. I should be able to plug in a USB 3.0 SSD and import data to a pool at NATIVE speed. I should be able to plug in a drive and dump or replicate data to use in another system. I should be able to plug in a drive or cage and replicate a pool for offsite use. All of these are quite legitimate uses for USB 3.0. All of these are easily done on other platforms, including some with ZFS.

That does NOT mean you buy a couple cheap pos usb drives, and hook them up to a garbage hub, build a multi-device pool on it and expect it to be as reliable as SAS. It won't be... and that is where the usb is not reliable argument plays.

At this point, it seems your best external option is hot-swap sata/sas. Non redundant zfs pools are a concern. Consumer hot-swap is a concern. So you better get to know your hardware and do testing on the bench. The touted best practice of shutting down before removing a drive is something to consider. E-sata is an option... but hard to do without port multipliers or single devices. So ymmv.

At this point, I back up externally by syncing to a USB cage on my client. Similar to DrKK. But it pisses me off that it has to go over the network. On the larger server, I have enough slots to insert and pull a backup pool. All of it feels pretty klunky. Of course we'd all love a second and third offsite server to replicate too...

This will be fixed in a later version with solid drivers. Might already be great in 9.3 but I haven't tested it.

 

[dtom10]

Ok, let me clarify some of the points stated in the replies.

USB3 is not enabled by default but the manual tells you how to enable it without any disclaimers that it may corrupt your data if you try to use it.

Why I need a solution to backup data from my NAS using USB3? My client which is an old Sandy Bridge laptop with Win7 x64 on it doesn't have USB3. A backup could take a very long time even if I use something like rsync which at this point I havent researched yet as a possible solution.

The NAS machine is a HP Microserver Gen8. No e-sata support, no hot-swap support.

The external drive is a WD Mybook 3TB. Not a cheap piece of hardware and so far I haven't had any problems with it or my other two WD Mybook external hdds.

So, the question remains: is it possible to create a striped zpool on the 3TB external drive, import it, replicate the NAS zpool and detach the drive?

 

[mjws00]

As far as I can tell your Microserver lacks ecc, and has a lynx point chipset. So if you enable usb3.0 how are we to know if it will work? It probably won't, but maybe this has been fixed. In addition the MyBook is not known for its robustness. Most of us don't comment on specific hardware we don't run, unless it is a VERY common known good set up.

*IF* usb3.0 works on your machine. You can use the device in a pool. But it has no redundancy, and ZFS may not respond how you want if it detects an error with no way to repair it. Thus the 'not recommended'. It is certainly possible as EricLoewe stated earlier. But it relies on assumptions few of us can make on your behalf.

Try it. Test it. Decide if you wish to continue using it.

 

[Ericloewe]

Ok, let me clarify some of the points stated in the replies.

USB3 is not enabled by default but the manual tells you how to enable it without any disclaimers that it may corrupt your data if you try to use it.

Why I need a solution to backup data from my NAS using USB3? My client which is an old Sandy Bridge laptop with Win7 x64 on it doesn't have USB3. A backup could take a very long time even if I use something like rsync which at this point I havent researched yet as a possible solution.

The NAS machine is a HP Microserver Gen8. No e-sata support, no hot-swap support.

The external drive is a WD Mybook 3TB. Not a cheap piece of hardware and so far I haven't had any problems with it or my other two WD Mybook external hdds.

So, the question remains: is it possible to create a striped zpool on the 3TB external drive, import it, replicate the NAS zpool and detach the drive?

It's certainly possible. Depending on your hardware, you might not be able to use USB 3.0, though.

I'm not familiar with the implications of repeatedly mounting and dismounting the new pool, but the lack of scrubs comes to mind as potential problem.

Reliability of USB is not quite at SATA levels, that's where most of the "don't use USB" advice comes from. There's a lot of dust that needs to settle around USB 3.0 and new protocols it introduces before the long term picture can be painted. USB 3.1 seems to add even more protocol confusion, unfortunately.

 

[dtom10]

Microserver has ECC memory and works only with ECC memory. That being settled, onwards to the USB3 :)

I DID successfully connect the MyBook drive to the Microserver and shared its NTFS filesystem data via CIFS. Granted NTFS is not a good option to use as already explained to me. Mostly because the proprietary nature of the filesystem prevents people to write good/reliable drivers for it. This is the reason why I came up with this nonsense approach to use ZFS on my external drive. And this situation is created by the fact that I try to avoid a laptop hardware upgrade and have USB3 on it :)

From what everybody is telling me so far I get that I try to use a NAS the way its not meant to be used. Although not recommended what I try to establish, being a noob in this department, is if my way of doing things is possible.

At the moment I got the following:

1. RAIDZ is a poor choice because of the low redundancy and lesser performance in comparison to RAIDZ2. The usable space difference is large in my case and before I sift through the terrabytes to reduce the data amount I need to store that's what I can afford right now.

2. ZFS on the external drive is a bad decision as only one URE will cause a total data loss. Am I correct in my assumption?

3. Using NTFS and backing up the NAS using a windows client machine will take a loong time due to USB2(only) availability on my client machine but afterwards I can sync/update the backup as I go. Seems to be the best option so far.

Let me know your thoughts on this. Thanks!

 

[cyberjock]

I find the USB is not reliable excuse tiresome. Fact is lynx point broke the FreeBSD USB 3.0 drivers. So the decision was made to pull support by default so people with shiny new Haswell boxes could still boot. That is all.

That is most certainly not all. USB was a bad idea back before USB3 was released. Do not be fooled. That's *not* the whole story.

The rest of the story involves things like:

1. USB not properly disconnecting itself from the system.
2. SMART not always functioning.
3. On a *single* disk error a disk will disconnect from the host system (aka the disk goes UNAVAIL).
4. USB can reorder the writes in a way that can result in pool corruption.

I'm sure there's more, but I've made my point. USB, as a technology is a terrible idea for servers.
Call Nexenta, Netapp, or the others and tell them you want to pay for a system that runs entirely on USB. They'll laugh at you while hanging up the phone. It's not a problem on FreeBSD. It's that USB, as a technology is inappropriate.

If you don't like that answer, sorry. Not here to sugar coat and give a false sense that data is secure. Feel free to go back to posts made before USB3 and Lynx Point was released. You'll see the same responses from back then.

There are many cases where USB is an excellent solution, and also some where it is poor. There are also "great" USB chipsets and devices, and "poor" USB chipsets and devices. They didn't break this on purpose or make a conscious decision to remove external USB drive support because it is "Bad".

Please reread what I wrote above. The USB technology itself is not designed to function the way ZFS works.

This is a significant weakness on the platform. Period. I should be able to plug in a USB 3.0 SSD and import data to a pool at NATIVE speed. I should be able to plug in a drive and dump or replicate data to use in another system. I should be able to plug in a drive or cage and replicate a pool for offsite use. All of these are quite legitimate uses for USB 3.0. All of these are easily done on other platforms, including some with ZFS.

Yep, and if you start talking to the more experienced users, they'll tell you the same thing. ZFS and USB really shouldn't mix. For reasons that are inside the silicon and not because "we don't like it".

 

[mjws00]

I've seen your opinion, cyber. It seems very limited in your definition of "server" and "terrible idea." Not everything requires ZFS. Not every external use requires absolute reliability. In the real world we frequently dump 1-2TB externally to move it via USB 3.0. It is done quickly and easily, and many times faster than the wire. The silicon is fine, ZFS may be a poor match. But BSD and UFS certainly can. Not to mention a few million windows servers and boxes. In addition to checksum or whatever means you choose to validate your data should you find that paramount.

With solid drivers I could certainly use a USB device as reliably on FreeNAS as FreeBSD or any other platform. That doesn't make it inappropriate. It simply makes it better for some things than others.

I do like the additional info on the rest of the story. I question the bias and sample sizes. I can find 100 reasons why Broken USB on FreeNAS is a huge competitive disadvantage and not a design decision. I'm not under obligation to make excuses for it.

 

[dtom10]

Ok, in my context, as a home user, I can cope with losing one or more files. So, ZFS cannot offer a reliable way of storing data if I'm comfortable with losing several files should the drive misbehave for whatever reasons, USB or drive failure. The best way remains to have a NTFS based copy made on the client machine on the USB external drive?

I was hoping to use the replication feature of ZFS to make the process as quick and painless as possible but I can always use windows alternatives if that's a better way.

 

[mjws00]

It would be great if zfs replication worked like that and was reliable on a single drive. It isn't. The problem is you likely don't get a corrupt file, you get the entire pool on the drive being unavailable. Unfortunately we can't write NTFS reliably from FreeNAS. So if you want a "read anywhere" copy you are kinda stuck. That's why some of us write from the client. Though in your case with only usb2 that is brutal.

Unfortunately it is what it is. For me the trade-off of having ZFS, outweighs the con of not having that tool available to me. I just went with the other options mentioned and didn't think twice. And lest you think I'm saying plug in that single drive and zfs it up... I'm NOT.

 

[cyberjock]

You won't lose "a few files". You'd lose the whole pool.

 

[wazaus]

From an end user point of view I have to agree with mjws00. I have a usb backup running with a raidz2 main data pool and it was working well until the external enclosure died (drive was ok).

When I first set up my server I had to learn so much just to get this simple aspect of the backup practice working. And now that I am using a different USB ext enclosure, if I try to reboot the server it hangs when it comes time to disconnect the external drive.

A lot of people want to use the best software available but don't have the budget for two dedicated server backups. USB is cheap and readily available if either part dies. I think more should be done to support it until a better solution becomes more cost effective and widely available.

If it wasn't for the undeniably superior data protection offered by zfs I am pretty sure I would have a different solution all together.