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Forum Discussion
XRAID turned RAID5 into RAID6 when adding a drive
When I added a drive, my RAID5 config changed to RAID6. Is it supposed to do that?
Danthem wrote:
"X-RAID® dynamically changes raid RAID1 for 1 - 2 drives. RAID5 for 3 - 6 drives. RAID6 for 7+ drives"
I agree with the logic (though I wonder what would happen if that conversion required shrinking the volume size - which could be required if the drives aren't the same size).
But I think there should be a confirmation on the UI before the conversion happens.
It's not sensible to use RAID-5 with that many disks.
The volume wouldn't be shrunk. Attempting to shrink a volume is dangerous.
mdgm wrote:
It's not sensible to use RAID-5 with that many disks.
I agree. But I still think a UI confirmation is a good idea. Once it converts, there's no going back. And a user who really needs the capacity might prefer to switch to flexraid, and set up a jbod volume instead.
mdgm wrote:
Attempting to shrink a volume is dangerous.
Understood. So what does happen if I have 2x6TB+4x4TB, and then I add a 6 TB drive to the array?
StephenB wrote:
Understood. So what does happen if I have 2x6TB+4x4TB, and then I add a 6 TB drive to the array?You start with 2x6TB + 4x4TB in RAID5, so you have one RAID5 of 6 partitions of 4TB (equivalent to 5 capacity + 1 parity), and one RAID5 of 2 partitions of 2TB (equivalent to RAID1, 1 capacity + 1 parity).
When adding a 7th HDD of 6TB, you reshape the first RAID5 of 6 partitions of 4TB to a RAID6 of 7 partitions of 4TB (equivalent to 5 capacity + 2 parity, so same capacity), and reshape the second RAID5 of 2 partitions of 2TB to a RAID6 of 3 partitions of 2TB (equivalent to 1 capacity + 2 parity, so same capacity).
jak0lantash wrote:
StephenB wrote:
Understood. So what does happen if I have 2x6TB+4x4TB, and then I add a 6 TB drive to the array?You start with 2x6TB + 4x4TB in RAID5, so you have one RAID5 of 6 partitions of 4TB (equivalent to 5 capacity + 1 parity), and one RAID5 of 2 partitions of 2TB (equivalent to RAID1, 1 capacity + 1 parity).
When adding a 7th HDD of 6TB, you reshape the first RAID5 of 6 partitions of 4TB to a RAID6 of 7 partitions of 4TB (equivalent to 5 capacity + 2 parity, so same capacity), and reshape the second RAID5 of 2 partitions of 2TB to a RAID6 of 3 partitions of 2TB (equivalent to 1 capacity + 2 parity, so same capacity).
https://i.imgur.com/jn2KmAG.png
jak0lantash wrote:
StephenB wrote:
Understood. So what does happen if I have 2x6TB+4x4TB, and then I add a 6 TB drive to the array?You start with 2x6TB + 4x4TB in RAID5, so you have one RAID5 of 6 partitions of 4TB (equivalent to 5 capacity + 1 parity), and one RAID5 of 2 partitions of 2TB (equivalent to RAID1, 1 capacity + 1 parity).
When adding a 7th HDD of 6TB, you reshape the first RAID5 of 6 partitions of 4TB to a RAID6 of 7 partitions of 4TB (equivalent to 5 capacity + 2 parity, so same capacity), and reshape the second RAID5 of 2 partitions of 2TB to a RAID6 of 3 partitions of 2TB (equivalent to 1 capacity + 2 parity, so same capacity).
https://i.imgur.com/jn2KmAG.png
jak0lantash wrote:
StephenB wrote:
Understood. So what does happen if I have 2x6TB+4x4TB, and then I add a 6 TB drive to the array?You start with 2x6TB + 4x4TB in RAID5, so you have one RAID5 of 6 partitions of 4TB (equivalent to 5 capacity + 1 parity), and one RAID5 of 2 partitions of 2TB (equivalent to RAID1, 1 capacity + 1 parity).
When adding a 7th HDD of 6TB, you reshape the first RAID5 of 6 partitions of 4TB to a RAID6 of 7 partitions of 4TB (equivalent to 5 capacity + 2 parity, so same capacity), and reshape the second RAID5 of 2 partitions of 2TB to a RAID6 of 3 partitions of 2TB (equivalent to 1 capacity + 2 parity, so same capacity).
https://i.imgur.com/jn2KmAG.png
Clearly dual redundancy is possible with three partitions - either via RAID-6 or triple-RAID-1. But so far, XRAID2 has never provided dual redundancy unless the four largest drives in the array are the same size.
Is your answer theoretical, or did the NAS actually create a 3-partition RAID-6 array for you? Note I am interested in knowing what it really does, not what is possible to do.
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