[SOLVED] RAID on slackware15.0, zfs or mdadm + ext4?

henca · 03-23-2023, 01:51 PM

Quote:

Originally Posted by LuckyCyborg

The consistency is detected by MD engine automatically and also automatically happens the array rebuilds and/or disks kicking.

I am not a programmer (to know precisely how MD driver works), but I guess that on the RAID1 the data read from both stripes (on each disks) should be equal, otherwise starts rebuilding the array. BUT, I believe that RAID1 has no way to check IF the equal data from stripes is correct or not. Anyway, any RAID1 system, no matter if it's software or hardware, should react this way.

That's why I believe that RAID5 is superior, because it has checksums for every data stripe, so eventually it even can rebuild the missing data. For example, introducing (replacing a faulty) disk in a 3 disks RAID5 will end with rebuilding your entire data correctly.

The parity stripe in a RAID5 system will be able to rebuild a single broken stipe, but it does not say which stripe is broken. The raid system will need to rely on the disks telling when they are broken and give read error. The same applies to RAID1, if a stripe would differ but both disks would say that they are OK RAID1 would not be able to solve that problem.

Usually hardware raid is to prefer instead of software raid. The OP got a degraded aray from his hardware RAID controller, but that does not for sure mean that the RAID controller is broken. Maybe one of the disks in the RAID1 array reported so many SMART errors that the controller decided to replace it. Instead replacing the controller and start using software RAID on the same disks might be a bad idea...

regards Henrik

wingfy01 · 03-23-2023, 09:47 PM

Quote:

Originally Posted by henca

The parity stripe in a RAID5 system will be able to rebuild a single broken stipe, but it does not say which stripe is broken. The raid system will need to rely on the disks telling when they are broken and give read error. The same applies to RAID1, if a stripe would differ but both disks would say that they are OK RAID1 would not be able to solve that problem.

Usually hardware raid is to prefer instead of software raid. The OP got a degraded aray from his hardware RAID controller, but that does not for sure mean that the RAID controller is broken. Maybe one of the disks in the RAID1 array reported so many SMART errors that the controller decided to replace it. Instead replacing the controller and start using software RAID on the same disks might be a bad idea...

regards Henrik

Thanks. The disks used for hardware controller before are all new disks bought from official and tested successfully with badblocks command.
The hardware raid controller could not find the second drive(always the second drive):
cable p1 connect to disk 1 (detected)
cable p2 connect to disk 2 (not found)
and
cable p1 connect to disk 2 (detected)
cable p2 connect to disk 1 (not found)
and
cable p2 connect to disk 1 (detected)
cable p3 connect to disk 2 (not found)
....
And i dont have much time to figure out the problem
And the card very very hot....very hot that i dont know if it is related to the problem.
And the card chip is very old but newer is very expensive....

So in my case...i think soft raid is the better for me....

And at last i choose mdadm + ext4.
There are so many tools that could be used for recover the disk with ext4 if the md was broken...