Hello everyone!

 

Now, to the point of my thread! I currently have a rather powerful homeserver, 8 cores, 64 GB ECC, 6x 2 TB disks in a Fractal Design Nova case, Mini ITX. Currently running FreeNAS

 

I have a lot of power here, and while this is good for streaming plex over the network, it usually just goes to waste because its idle 98% of the time.

 

So what I wanted to do, was this:

Sort of have dual protection, is it actually possible? Like can I create 2 drive pools of 3 disks, 6 disks in total. Then have those two protect each other?

 

I want this, because currently with RAIDZ2, I can loose two drives without dataloss, now I want the added functionality of running UnRAID so I can have a few Windows VMs for when I work away from my desk. But also have a pool of drives for media storage.

 

So is it possible to have 2 drive pools be each others backup? So if two drives fail in one pool, the other pool got its back, and if one fails in each the parity protects both?

On Unraid you can have one drivepool as you refer to it, with one parity disk currently.

 

Dual parity is planned in the next release which we expect soon, but have no further details on exactly when.

I feel ya, but is it only possible to have a single drive pool?

 

Say I was to have a script run every day at midnight that basically copy paste all data from one pool to the other?

You can have a single parity protected array, and an unprotected cache array, but that isn't really what you're after.

Okay, say I have my 6 drives.

 

I want to run 2 VM's, one Windows for work and one Linux as testing ground.

 

I also want 4 shares, one media for Plex, one private for science experiements, one read only for say installers like Adobe n stuff like that.

 

Firstly is this possible to do?

 

Now I backup all my extremely important data 4 places, so backup is not the issue here. But it always sucks to loose data.

 

Say I go on vacation and halfway through the week 1 drive fails. I shut it down remotely using my VM, and return home. At home I find out that 2 drives actually failed.

If these two drives was data drive and the parity, what would happen. What if these drives was both data drives? Would it all be gone no matter what?

As CHBMB noted, the answer to your question is No.

 

However ... as was also noted, dual parity is almost certainly going to be in the next UnRAID release, so you'll be able to lose 2 drives without data loss (as you can now) => so you could have the same level of protection you now have alone with the ability to use VM's and other UnRAID features.

 

... You could also set up a protected array and a btrfs cache pool, and treat the cache pool as a "backup" for your protected array.  This would provide fault tolerance for BOTH the protected array and the cache ... and as long as your shares were NOT cached the cache pool would be effectively a separate fault-tolerant storage array.  This would in effect be what you've suggested ... and if you used 2 parity drives the primary array would have dual failure protection.

 

... Say I go on vacation and halfway through the week 1 drive fails. I shut it down remotely using my VM, and return home. At home I find out that 2 drives actually failed.

If these two drives was data drive and the parity, what would happen. What if these drives was both data drives? Would it all be gone no matter what?

 

Once dual parity is implemented (almost certainly in the next release), two drive failures would not result in any data loss.    Doesn't matter which two drives fail.

 

... Say I go on vacation and halfway through the week 1 drive fails. I shut it down remotely using my VM, and return home. At home I find out that 2 drives actually failed.

If these two drives was data drive and the parity, what would happen. What if these drives was both data drives? Would it all be gone no matter what?

 

Once dual parity is implemented (almost certainly in the next release), two drive failures would not result in any data loss.    Doesn't matter which two drives fail.

 

I see that, but I'm asking is this like raid. Where if it fails its all gone, or would I be able to basically plugin a power and sata cable to the still working drives and recover them despite the 2 fails?

Why dont people read before asking tons of questions?!?!?!

Its not like conventional raid, if both your parity drives fail, your array becomes unprotected from further failures, but it keeps on running and you don't lose any data, you just replace your parity drives and let it rebuilt them. If you suffer an additional third drive failure then you only lose the data on that drive.

http://lime-technology.com/what-is-unraid/

... Say I go on vacation and halfway through the week 1 drive fails. I shut it down remotely using my VM, and return home. At home I find out that 2 drives actually failed.

If these two drives was data drive and the parity, what would happen. What if these drives was both data drives? Would it all be gone no matter what?

 

Once dual parity is implemented (almost certainly in the next release), two drive failures would not result in any data loss.    Doesn't matter which two drives fail.

 

I see that, but I'm asking is this like raid. Where if it fails its all gone, or would I be able to basically plugin a power and sata cable to the still working drives and recover them despite the 2 fails?

 

Yes/No You maybe able to plugin to another machine and use a Linux driver and extract the data. Since data is stored on each Drive independently from the OS you might get lucky, but to say you can just plug in a cable and read away is hard to say honestly. Depends on the failure. If the drive is so bad its unreadable then no.

... I see that, but I'm asking is this like raid. Where if it fails its all gone, or would I be able to basically plugin a power and sata cable to the still working drives and recover them despite the 2 fails?

 

r.e. "... despite the 2 fails ..."  => If you only had two drives fail, you won't lose ANY data.    With dual parity the system is fault tolerant for up to 2 drive failures.    If, however, a THIRD drive was to fail, then Yes, you'd still be able to read the data on the "still working drives".

 

How much data you'd actually lose would depend on which 3 drives failed -- if two of those were the two parity drives; then you'd only lose one drive's worth of data.    If, of course, all 3 were data drives, then you'd lose all of their data.

 

It's also possible, of course, as with any failed drive; that you may be able to recover some of the data on failed drives using data recovery software or professional data recovery services.

 

 

Please read this and you will probably be able to ask much better questions.

http://lime-technology.com/what-is-unraid/

I see that, but I'm asking is this like raid. Where if it fails its all gone, or would I be able to basically plugin a power and sata cable to the still working drives and recover them despite the 2 fails?

 

Yes/No You maybe able to plugin to another machine and use a Linux driver and extract the data. Since data is stored on each Drive independently from the OS you might get lucky, but to say you can just plug in a cable and read away is hard to say honestly. Depends on the failure. If the drive is so bad its unreadable then no.

 

I think kizer interprets this differently to me, if you have a five drive array with one parity disk and you lose both parity & one of the disks, you would indeed be able to access the data from the remaining four data drives...

A point that often does not get emphasised enough is that since every disk is a discrete filing system, even after a disk 'failure' at the unRAID level (which is often just a failed write) if the disk has not physically failed then most of the data off it can normally be retrieved.

I think kizer interprets this differently to me, if you have a five drive array with one parity disk and you lose both parity & one of the disks, you would indeed be able to access the data from the remaining four data drives...

 

CHBMB is Exactly right.......

 

I'm talking about the failed discs you can still work with them to get your data off... Just depends on how failed they are. There's unRAID deems them unacceptable vs lets attempt some data recovery with the use of some Linux tools or paid professionals.

 

Honestly having a Pre-cleared spare on hand, Parity checks monthly or when Big system wide changes are made and watching your SMART reports are good practices and honestly should put a lot of worry to rest until Dual Parity arrives.

I think kizer interprets this differently to me, if you have a five drive array with one parity disk and you lose both parity & one of the disks, you would indeed be able to access the data from the remaining four data drives...

 

CHBMB is Exactly right.......

 

I'm talking about the failed discs you can still work with them to get your data off... Just depends on how failed they are. There's unRAID deems them unacceptable vs lets attempt some data recovery with the use of some Linux tools or paid professionals.

 

Honestly having a Pre-cleared spare on hand, Parity checks monthly or when Big system wide changes are made and watching your SMART reports are good practices and honestly should put a lot of worry to rest until Dual Parity arrives.

 

I think it was possible to interpret in two different ways and I think we both are right....