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replacing a dying drive

Ludovic1
Aspirant

replacing a dying drive

Hi,

 

I have a ReadyNAS Ultra 2, with 2 disks of 2TB.

 

One of the disks appears to be dying (saw some errors in the logs), though it's not completely dead yet.

 

Because of this, the ReadyNAS no longer seems to boot. But by booting it in tech support mode and telneting into it, I was able to see the data was still there on (at least) 1 drive, and after doing that and rebooting, the ReadyNAS all of a sudden was able to boot normally, and it copied the data from disk 1 over to disk 2 (the broken disk) again.

 

The ReadyNAS worked fine for a couple of days, and I kept using it while the replacement drive was on its way from Amazon.

 

Now, the ReadyNAS doesn't boot again, so I guess I'll have to start it in tech support mode again, telnet into it, reboot it, and hope it works again.

 

My questions are:

1) Is it normal that the ReadyNAS doesn't boot anymore when a disk is dying?

2) How does the ReadyNAS determine which disk is good? E.g. it copied everything from disk 1 back to disk 2, but I suppose the reverse could've happened as well -- thereby destroying disk 1?

3) To replace a disk, do I only need to swap my dying disk with a new one, then boot the NAS? Will the NAS take care of formatting the new disk correctly, etc.?

 

Basically, I'm concerned that the ReadyNAS makes a wrong decision, and decides to overwrite my last good disk... (As I don't have another backup, unfortunately.)

 

Thanks a lot for sharing your expertise!

 

Model: ReadyNASRNDU2120|ReadyNAS Ultra 2 2TB (1 x 2TB Desktop)
Message 1 of 5
JennC
NETGEAR Employee Retired

Re: replacing a dying drive

Hello Ludovic1,

 

If the steps you usually take does not work this time, try Skip Volume check from boot menu. Once you are able to get to the admin page, download the logs and check the disk health (ATA errors increasing and Reallocated sector errors).

 

It is possible that not only one disk is faulty. Always have a full backup, that's what we always recommend. Because if there are more than just 1 disk get faulty in a 2-bay NAS or a 4-bay NAS with XRAID, that is a problem.

 

The OS, settings and data are stored to the disks that is why if one disk get faulty, and the other one is not healthy enough booting up sometimes get problem.

 

See How do I replace a disk in my ReadyNAS Ultra, Ultra Plus, NVX or Pro series storage system? article for replacing disks.

 

Regards,

 

Message 2 of 5
mdgm-ntgr
NETGEAR Employee Retired

Re: replacing a dying drive

You could boot the NAS with just the good disk installed and once you've confirmed that it's come up fine and that the disk is healthy add the new disk while the NAS is on.

Message 3 of 5
Ludovic1
Aspirant

Re: replacing a dying drive

Hi Jenn, mdgm,

 

Thanks for your help, that gets me further.

 

I still have one question/doubt: how does ReadyNAS identify which drive is the good one? So how does it know to sync from drive 1 to drive 2, and not the other way around?

 

(Especially if both drives are damaged, there's a risk of losing data if ReadyNAS starts syncing from one to the other. Though I will probably just remove one of the drives before booting.)

 

Thanks!

Message 4 of 5
StephenB
Guru

Re: replacing a dying drive

You can look at the SMART stats to identify which drive is dying (there are some freeware tools that will let you do this on a PC too - acronis drive monitor is one).

 

In general, the NAS will sync the already installed drive to a newly inserted drive.

 

There are also RAID event counters stored on each drive, though I don't know exactly how those influence the decision.  I do know that if the counters are seriously mismatched the volume won't be mounted at all.

If you are concerned about both drives failing, then you should clone one (or both) to healthy drives before you begin.

Message 5 of 5
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