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RAID disks, errors, etc.
I have an ATTO controlled RAID 6 (8 drives). When it discovers a volume (disk) with a bad sector, the management app notifies me, and warns it may be going to fail soon. I can keep working. I’ve apparently lost no data, but I will keep getting the messages continuously until I put in a fresh drive and let the RAID rebuild.
I’ve read up on bad sectors and how to fix them on Mac OS – erase the drive using one of the security modes that writes zeros over the entire disk. During the process, bad sectors are mapped and skipped by the OS.
So, my questions are:
1. Once I’ve removed a drive with a bad sector from my RAID, and reformatted it to map out the bad sectors, what happens if I use that as a replacement disk the next time ATTO tells me I have a disk with errors?
2. When I replace a drive in my RAID, I don’t format it first. I take it from the packaging, put it in the RAID, tell the control app that’s a new volume for the RAID, and it starts rebuilding itself. So, is the fact I mapped out the bad sectors in Disk Utility ignored by the ATTO Control? Or, does it somehow “know” that a bad sector has been mapped out? I’m thinking not, but I’m not an expert at this.
I can use the reformatted former RAID disks for single disk backups or whatever. But, once disks start failing in a RAID (naturally, after the warranties expire), seems like it’s a matter of time before they all fail. I’m on my third replacement for this particular group of drives, which means I have three 12 TB disks that are functional, but may not be suitable to put back in my RAID.
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5 Replies
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To answer question 1: I believe if you mapped out the bad sectors after reformatting, it should be read as a brand new replacement disk and shouldn’t get any errors. If it does, maybe something may be physically faulty with that drive and will have to be replaced with a brand new one.
Question 2: I am not sure if the bad sector would get ignored by ATTO control, but like I said, if you mapped out the bad sectors, it should be read as a brand new disk and should be part of the RAID getting ready to see incase one other RAID goes bad, the extra blank disc can be use to duplicate and back up another drive that can become faulty so you always have the backup of the important data. Thats what I believe. I am pretty new with the ATTO control myself but I have studied RAIDs before and its really good at backing up data between multiple hard drives.
Question, since you said that you are on your third replacement, how often does a drive fail in a raid and do you know the cause of the bad sectors on them?
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Also for more info on RAIDS for the future, I recommend you look into this: https://www.youtube.com/watch?v=A_UXW9lUCxY
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I know nothing about any of this but I have an idea. Can you tabulate how many total bits, or disk memory before and then after and see if it has changed any? If it has changed and in theory would be lower than before, then perhaps one could assume the disk has figured out how to ignore the bad spots. If the amount is identical before and after, not sure what that would mean.
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Hector, sorry for the late reply. I must have disabled notifications for responses.
To answer your first question: I believe the drives are producing errors because they are old, and have been spinning almost non-stop since installation, and I’m using the RAID almost daily and all day long for video editing and DAW functions. So, nothing completely unexpected. Drives fail. That’s a fact of life.
But, these aren’t complete disk failures. This is about notifications I get from ATTO Config that it has detected errors.
I think what I can do to learn for myself is to replace a drive with a reformatted one for which I’m mapped out the bad sectors, let the RAID rebuild, then run a verify pass to see if ATTO Config fingers the same drive for having errors. That would take me around three to four days. Rebuilds take about 12 hours and verifies take about 24. I’d need plenty of downtime for that, which I don’t have at this point, which is why I asked the question here on this forum.
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Allesandro, I can give your suggestion a try the next time I get a drive error. I expect this will be fairly routine now that most of the original drives have several years of mostly constant usage.
A silver lining is that I can still find new drives of the same model for about a quarter of what I paid for them when I first installed all eight 12 TB drives.
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