1 of 3 Drives dead - is data recovery Possible?

[regraham]

Hi All, Several years ago I installed FreeNAS on an old HPEX495 Media Centre - I followed, well, I actually wrote this guide....this guide....

I installed 9.2.1.5 and for anyone who knows the EX495, you may be aware that I installed this blind since I had no way of connecting up a monitor...ok

I used the system less and less over the years and about a year ago when I went to check it, I realised FreeNAS was not booting as I could not access the web interface anymore. I could still see it in my Router as a connected device but I could not see the web admin page.

I popped out the drives and plugged them into my Windows PC to see if I could tell anything, lo and behold, one of them was not recognised. it's dead.

I've no idea now if i set this up as ZFS or UFS as I think there were some limitations with ZFS due to the hardware at the time. But I'm sure I would have spanned the data to have 1 big 6TB drive (3x 2TB).

Now most of this stuff is crap media files for a media server, but a good chunk of it is personal photos and my wedding video.

1. Is there any way to recover this since one drive is dead?
2. How do these systems store data, is a whole file stored on one drive or is the data for a single file spread across all 3? (If the latter is there any kind of parity index to restore them from the remaining 2 drives?)

 

[sretalla]

I would have spanned the data to have 1 big 6TB drive (3x 2TB)

1. Is there any way to recover this since one drive is dead?

Probably not in full, but you may be able to use a tool like Klennet (https://www.klennet.com/zfs-recovery/default.aspx).

It's not free, but you can run it to see what will be recovered before paying, so only time lost if it's not going to work.

There's also an "open source" option, which may or may not provide some options to recover:

https://github.com/Stefan311/ZfsSpy

But if you're essentially missing 1/3 of the data, don't expect too much from it as an overall effort.

Best practice for both cases (although the second tool mandates it, I think) is to operate from image files of the disks, so you're not risking further damage as you go.

How do these systems store data, is a whole file stored on one drive or is the data for a single file spread across all 3? (If the latter is there any kind of parity index to restore them from the remaining 2 drives?)

If you used a stripe (which you seem to indicate), then blocks are allocated across the disks... some files may fit inside a block (perhaps the photos) or by some miracle all be contained on the living disks, so something may be possible, but as a general rule, what you find on the disks will not be whole/complete files,

If you had elected to sacrifice some data capacity to redundancy and gone with RAIDZ1, then you're in business... you have the parity or original data to get all of it back with only 2 of the disks... but your pool would probably also be able to mount, so it seems that case is unlikely.

I popped out the drives and plugged them into my Windows PC to see if I could tell anything, lo and behold, one of them was not recognised. it's dead.

Windows doesn't know how to interact with ZFS, so that's not a surprise... I hope you opted out of the initialization step in Windows, which may have made the rest of the job harder if you did that.

 

[Constantin]

A Z1 ZFS array would only have given you 4TB of usable storage capacity... so if you had 6TB available, you must have created a 3-way stripe drive? (i.e. RAID 0) As Sretella points out, the recovery options are limited if the files were written out across multiple disks... which seems likely for larger files like photos or your wedding video.

I hope I'm wrong but it looks like you might be becoming a data recovery customer in the near future if those pictures, video, etc. are worth it to you. However, I'd ask the demi-gods here first whether/how a "reconstituted"/recovered stripe drive can be re-integrated into a RAID 0 array. I don't know how picky ZFS is about the specific disk structures of drives in a stripe array.