ReadyNas NV+ v2 stuck on boot menu

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tomupnorth wrote:

Bah, I'm sorry I forgot you were in Oz. I'll bet any local small repair shop guy can do with Linux Reader to look for and recover your pics.

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FWIW, you are assuming that the RAID array is in sync, so there is no need for recovery.

That could be the case, but it is very possible that there is a need to do more before the array can be mounted.  

Don't understand StephenB. If the disk partitions are intact, the data can be found. No?

Explain it to me like I have no idea what it means for a RAID array to be in sync--and what it means to simple file recovery if it is not.

My thought is not to "mount the array" at all.

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tomupnorth wrote:

 

Explain it to me like I have no idea what it means for a RAID array to be in sync--and what it means to simple file recovery if it is not.

 

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With RAID-5, the data is spread across all 4 disks.  This is done by "striping" - you can visualize it by thinking of the 4 disks as cylinders that are arranged on a table, and then thinly slice across them to create the stripes.  Each stripe contains one parity block  - and the stripes are constructed so parity blocks are also spread across all 4 disks.  For instance, the first stripe might put the parity on disk 4, the second on disk 3, etc.

When you write to a large file to a RAID-5 array, that file won't physically be on one disk - it will be spread across more than one.  And every write (even if small), requires an update to at least one parity block - which is always on a different disk than the data.  The folder structure of the volume won't be stored on one disk either - it will be spread around.

Disk writes are cached for performance reasons, so if the NAS loses power or crashes, some writes will be lost.  When this happens the array is out of sync.  Some file data will be missing (never written), and some parity blocks won't be correct (never updated).

RAID systems detect this using transaction counters that are stored on each disk. If the transaction counters differ, then the RAID system is out of sync.  If it is out of sync, then you do need specialized tools to try and reconstruct it (and even with those tools, there will usually be some data loss).

It is different if you are using RAID-1 - which simply mirrors the two disks, so all writes are always done in parallel to both disks.  Generally speaking, RAID-1 recovery is much simpler, since all the data is normally on both disks.  There still can be some data loss due to cached writes, but this really isn't much different than a single disk system when the power has failed.

FWIW, I generally recommend UPS protection for ReadyNAS using RAID - this prevents unexpected power loss, which reduces the risk of lost writes when the power fails.  Of course this doesn't protect against the NAS crashing, but in my experience power loss is more common than crashes.  I also recommend that everyone have a backup plan in place, since all devices can fail w/o warning.  RAID isn't enough to protect your data, and RAID recovery is both expensive and uncertain.

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tomupnorth wrote:

 

My thought is not to "mount the array" at all.

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Linux Reader is mounting the array, and reading the ext file system that it holds.

Wow thank you StephenB. That is an awesome reply. So assuming the OP's 4-disk NV+ was formatted X-RAID, he has a RAID-5 system and thus files are spread-across the disks. And even if they are in-sync, the files wouldn't be individually readable on any one disk. Do I have that right?

I recently upgraded my own NV+ to 2TB disks, and the working 1TB disks are in a drawer. I am going to get them out and look at them again, as I obviously thought I'd seen individual files on the one that I looked at.

Assuming you are right, I will come-back here with hat-in-hand to apologize for dirtying OP's thread and adding to his consternation.

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tomupnorth wrote:

. So assuming the OP's 4-disk NV+ was formatted X-RAID, he has a RAID-5 system and thus files are spread-across the disks. And even if they are in-sync, the files wouldn't be individually readable on any one disk. Do I have that right?

 

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Correct. (though small files might be happen to fit on one disk)

One thing to keep in mind is that the ReadyNAS also has a small OS partition (4 GB). That holds Linux and the ReadyNAS application software.  That is mirrored on every disk - so Linux Reader will find that partition and the files on it.

Well, I'm embarassed. I could swear that I'd used Linux Reader (from DiskInternals) to see the file structures on one of my disks but...apparently not as I"ve tried again and it simply doesn't work. Shows the disk partitions but they do not open (not even the OS partition). I tried additionally to run the RAID Recovery tool from DiskInternals but it actually crashes on my system.

I apologize Jimmy112 for this distraction and false hope. I would delete all my posts (so as not to confuse any who may look here in the future) but that might just cause even more confusion. Glad StephenB knows his stuff and pushed-back on me!

I will be more careful "helping" here in the future!

🙁

Hi tomupnorth , StephenB , Sandshark , Marc_V 

Sorry for the lack of communication lately. I have since sent my NAS off to a data recovery company who are still working on it.

If it's taking this this long then I am 100% sure I would have messed it up trying to recover the data myself.

I might leave all the replies up as it might confuse people if I start removing anything and some of what Stephen B said could help someone else later down the track

I just wanted to end this by saying thank you for your help and advise. These forums are great for novices like me and experts like you being able to help out so thank you!!!

I hope you come back here and report; let us know if you can, what methods the recovery company used and of course success or fail.

Good Luck!