SOLVED raidZ hard disk failure

[Neeraj Saraf]

As I understand, in RAIDz a minimum of 3 drives are required. 2 for data and 1 to rebuild the data.
If one of the 2 drives fail, the 3rd drive rebuilds the data.

Question 1: If there are 3 drives of 1TB each on RAIDz with a usable capacity of 1.7 TB and filled to 50% capacity and 1 of the 2 drives fails. Approximately, how long will it take to rebuild the data in this case.

Question 2: What happens when the 3rd drive (for rebuilding the data) goes down?

Thank you.

 

[danb35]

The first question is going to depend on too many details to give a valid answer more specific than "a few hours, probably". But as to the second, in RAIDZ, the data and parity are stored across all the drives. Some very old RAID arrangements had one drive just for parity, but they were never used much, and aren't used at all with ZFS. Thus it doesn't matter which drive fails, as long as you don't have another drive failure before you finish rebuilding.

 

[Neeraj Saraf]

The first question is going to depend on too many details to give a valid answer more specific than "a few hours, probably". But as to the second, in RAIDZ, the data and parity are stored across all the drives. Some very old RAID arrangements had one drive just for parity, but they were never used much, and aren't used at all with ZFS. Thus it doesn't matter which drive fails, as long as you don't have another drive failure before you finish rebuilding.

Fabulous....

 

[depasseg]

Question 1: If there are 3 drives of 1TB each on RAIDz with a usable capacity of 1.7 TB and filled to 50% capacity and 1 of the 2 drives fails. Approximately, how long will it take to rebuild the data in this case.

I agree with @danb35. It in the couple hour range.

Question 2: What happens when the 3rd drive (for rebuilding the data) goes down?

If during resilvering, a second drive fails, then you lose everything. In RAIDZ2, you can lose a second during a resilver and be ok (but if you lose a 3rd disk, then you lose the pool data).

 

[danb35]

If during resilvering, a second drive fails, then you lose everything.

True, but I think the question was assuming that there were two data disks and one parity disk, a la RAID 3/4, where all the parity information is on one disk, and that disk failed.

 

[Neeraj Saraf]

True, but I think the question was assuming that there were two data disks and one parity disk, a la RAID 3/4, where all the parity information is on one disk, and that disk failed.

Yep..you got that right...

And made the working / functioning pretty clear.

Thanks to others too...