Any software raid specialists here?

Richard G

Richard G

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This is non-DA so hence here in the off-topic section, maybe somebody has a clue.

I have a NAS with raid 5. On changing a disk, things crashed.
Seems one of the disks (the one to be replaced) is stated as "Removed" and I only got /md0 and /md126 but /md1 (the raid volume) is gone.

So I guess I need to transfer the partition table to the new disk and then add the disk in the raid 5 again to get rebuilding started.
At least if this is the way to go.

But I don't know because I don't know a lot about software raid. And support said it's not repairable because one of the other disks is stuck in rebuilding.
I don't know either how to check that last part or if I can get any other way to rescue at least some of my data.

Most of the files are backup's so that is not an issue, but there are some other non-backup files which are less important, but if possible I would like to rescue them.
 
Raid5 = problems , you can try to force the raid online:

Mdadm recovery and resync - Thomas-Krenn-Wiki-en

The following article looks at the Recovery and Resync operations of the Linux Software RAID tools mdadm more closely. Here we will show you a few commands and explain the steps.
www.thomas-krenn.com www.thomas-krenn.com

Why was the reason for the disc replacement? Do you still have that disk?

You can try put the original disks, force the md online and try a resync.
 
dmtinc said:
Why was the reason for the disc replacement? Do you still have that disk?
Click to expand...
Why is raid 5 problems? I thought this was best for a NAS due to the redundancy of raid 5.

The reason for the replacement is that the disk became faulty. SMART gave a sector error and then automatically the raid is degraded. Since I had a new disk present, I replaced it.
I do still have the original (old) disk, but according to NAS support it's now empty without partitions. It was the 4th disk so that would be /dev/sdd if I'm not mistaken.

According to NAS support there was a short rebuild attempt later and now /dev/sdb so the second disk, is stuck in rebuild. In this case that would mean 2 faulty disk in raid 5 and no rescue is possible.

I will fysically check in another system if indeed all partitions on the old disk are gone. But I'm afraid this could be true.

As after I swapped the disk, and started the NAS the volume became inaccessible. So I put in the old disk again and it started rebuilding. When I've seen that, I hot swapped the old disk with the new disk, in the thought that this would rebuild too.
From that moment on, the raid volume was again inaccessible and this has not been fixed anymore, no rebuilding has taken place.
 
raid 5 allows only 1 failed disk, in your case you have 1 failed/replaced/clean and second failed during rebuilding of the first?
in such case you can try to restore raid with all old disks and then if rebuild passed successfully - try to replace disk again.
 
Zhenyapan said:
raid 5 allows only 1 failed disk, in your case you have 1 failed/replaced/clean and second failed during rebuilding of the first?
in such case you can try to restore raid with all old disks and then if rebuild passed successfully - try to replace disk again.
Click to expand...
YUP is often problem disks out of same batch , dying in same time slots.. :(
 
ikkeben said:
YUP is often problem disks out of same batch , dying in same time slots.. :(
Click to expand...
because at rebuild moment load increased, and sometimes it's enough to kill a drive that was on edge :(
that's why sometimes better to have 2 separate copies than to have mirrored raid.
but in production - raid 10 is the best, nowadays HDDs not so expensive, so if you bought 3 disks for raid5 - better to buy +1 and make raid 10.
 
Zhenyapan said:
in your case you have 1 failed/replaced/clean and second failed during rebuilding of the first?
Click to expand...
Correct.
But support said the old replaced disk has no partitions anymore hence 2 failed disks and won't rebuild.
I'm going to put the old disk on my pc and verify that indeed the partitions are gone.
2 years ago I already replaced one of the discs which really went faulty, so they are not all the same batch. But I understand what you all mean.

Zhenyapan said:
So if you bought 3 disks for raid5 - better to buy +1 and make raid 10.
Click to expand...
I have 4 disks for raid 5. Raid 10 was not an option in the NAS and raid 6 costed me too much room. In case of raid 6 you have the worth of 2 discs almost for striping. So now with 8 TB on space, I had 5 TB which I could use. With Raid 6 this would have been 4 TB. At time of bying those discs with the NAS it was around 870 euro's. Disks were 125 euro's a piece at that time.

It's for my personal use. I backup all my important things twice. Once on a NAS with raid 1, just all the files I really need.
On the raid 5 NAS every week a complete disk image is created. So the backups can be redone that is no issue. I always have 2 backups this way. And the original files.

But I also used that NAS for trainsim files and a bunchload of all my dvd movies which I converted and put on the NAS so I can look them at every TV in the house. This was around 3.5 TB. I just was thinking of upgrading to 4 TB disks.
For this purpose I don't know a better way to work.
 
Richard G said:
Correct.
But support said the old replaced disk has no partitions anymore hence 2 failed disks and won't rebuild.
I'm going to put the old disk on my pc and verify that indeed the partitions are gone.
2 years ago I already replaced one of the discs which really went faulty, so they are not all the same batch. But I understand what you all mean.


I have 4 disks for raid 5. Raid 10 was not an option in the NAS and raid 6 costed me too much room. In case of raid 6 you have the worth of 2 discs almost for striping. So now with 8 TB on space, I had 5 TB which I could use. With Raid 6 this would have been 4 TB. At time of bying those discs with the NAS it was around 870 euro's. Disks were 125 euro's a piece at that time.

It's for my personal use. I backup all my important things twice. Once on a NAS with raid 1, just all the files I really need.
On the raid 5 NAS every week a complete disk image is created. So the backups can be redone that is no issue. I always have 2 backups this way. And the original files.

But I also used that NAS for trainsim files and a bunchload of all my dvd movies which I converted and put on the NAS so I can look them at every TV in the house. This was around 3.5 TB. I just was thinking of upgrading to 4 TB disks.
For this purpose I don't know a better way to work.
Click to expand...
it's better to move to 6-8tb disks, this will give you enough space to grow up for few years.
 
Not for me as I don't use this NAS professionally, only for my ow business backups (disk images) on this NAS (and in file form on another NAS) and my movies.
The 4 TB disks costs 104 euro now, so that would be 416 euro for those disks alone. I'm only a very little company so this is not a little bit of money for me.

It's just pity of all the movies (will take days of work to convert again) and the trainsim addons that's why I'm trying to see if I can rescue some of it some way.
 
Yes one... I'm talking about 4 disks for raid 5. ;)
If 1 disk fails, always the chance to rescue. If one 12TB drive fails, you can start again no matter what.
Again I don't mind the backup but the files I store on it which I have no room for and not really important. But it saves loads of work if you they can be rescued.

I installed the system new now.
 
No problem at all, no need to be sorry. ;)
I could also have choosen to use a 12 or 16 tb usb disk only for backup now. So your suggestion is welcome anyway. :)
 
Sorry to hear Richard G, did you get this sorted?
I've only had issues with software Raid 5 in the past.
Never ever managed to get going again successfully with 4 disk software Raid 5 when I disk crashed.
 
Hello @istartcloud.
Yes I got it sorted... well... kind of. I build the raid again. It was a bit of my own fault that this happened and part of the NAS.

This caused it:
Richard G said:
So I put in the old disk again and it started rebuilding. When I've seen that, I hot swapped the old disk with the new disk, in the thought that this would rebuild too.
Click to expand...
Which as a wrong thought. I should have left it rebuild until it was finished.
A technician of the Asustor NAS had a look (great service these guys) and when I hot swapped the old disk, it stopt building, but 1 of the other disk got stuck in the rebuild. So when I put back the new disk, I had 1 empty disk (so non raid) and 1 stuck disk. If you have 2 "defective" disks in a Raid 5, you're done, you can start over.
I tried with the old disk, but since the raid start rebuilding, it lost it's data to rebuild, so that wouldn't give a "good" disk either anymore.

So that's a point to remember, when it starts rebuilding, don't touch it anymore.

I had it once before a year earlier, then I just hot swapped the disk and the rebuilding started, no issues.
Since then I got another NAS with raid5, a cheap one with second hand disks, I use that as backup for the first NAS. :)
Not really needed, but I like to play with NAS systems. :)
 
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