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Re: OT: Current_Pending_Sector on /dev/sd?




On 13.02.2019 18:22, basti wrote:
hello,
I have a raid6 with 4 disks. 2 of them show Current_Pending_Sector 1.
The disks has warranty till Apr. 2019 so I decide to replace them.

After I change the disk and install it on an other computer to overwrite
with zero it the Current_Pending_Sector is gone.

What should I do? Whats our experience?

Best Regards,

IMO, it's ok for disk devices to develop unreadable blocks (bad blocks), as long as they don't progress.
Internal firmware of the disk takes care of bad blocks, marks them internally and reallocates them. (makes sure that next read\write request to that bad block will be redirected to a safe block)
When internal list of bad blocks and reallocations will be full, firmware will mark HDD as failed in SMART.

As capacity of modern HDDs gets bigger and surface density of blocks increases, so does margin for error of faulty blocks. It is rare for a large disk to not have them, despite the fact that every disk was scanned and faulty regions remapped beforehand during manufacturing process at the factory.
HDDs that developed bad blocks should be monitored for progression and replaced if bad blocks began to appear frequently. You can get one bad block in 5 years or 30 in a few days and there is no guarantee that brand new drive won't have bad blocks.

Most hardware RAID controllers perform automatic full surface scans to ensure data consistency (also could be called "patrol scans") and mark HDDs as "Expected to Fail Soon" to warn user.
You have to backup your data regularly and in case of large RAID5/6 level arrays you should have at least one Hot Spare drive available in your enclosure at all times.
Precautions are almost the same for software RAID, but more difficult to setup.

-- 
With kindest regards, Alexander.

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