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 RAID6(6D+2P) OR RAID6(14D+2P) IS BEST ON VSP 5600?

G Gopi's profile image
G Gopi posted 09-12-2022 11:11
Hi Team,

Is RAID6(6D+2P) or 14D+2P is best while considering rebuild and resiliency etc ?  What is the rebuild time with 15TB nvme for both the RAID groups?
Carlos Mazaro's profile image
Carlos Mazaro
Both are good choices for resiliency, for rebuild time 15TB - correction copy time is 6 h 40 m for 6D+2P and in the case of RAID6 (14D+2P), the correction copy time of NVMe SSDs might be two times longer than described - with NO HOST I/O.
John Yarborough's profile image
John Yarborough
I also think about a concept of "RISK Pool" when making these decisions.  What if the worst possible scenario occurs and I have to restore all this? If the data on the disks are things like executive staff email I go with the smaller 6+2. Losing their mail can be a resume generating event.

When the data on the disks are things like regular users home directories I use the bigger 14+2. Yes they'll be lots of complaining while the restores are running but I'll survive that.
Sumit Keshri's profile image
Sumit Keshri
In terms of resiliency point of view, RAID 6 (6D+2P) would be the best choice when compared with RAID6 (14D+2P), because 6D+2P can sustain 2 drives failures out of 8 drives, but with 14D +2P configuration, it can sustain only 2 drives failure out of 16 drive.

The rebuild time in RAID 6 (14D+2P) will take lesser time because the data parity will be distributed across all the drives & all the healthy drives will be used in the rebuild operation. So, If you have a higher number of drives in the parity group, the rebuild operation would be quicker.
Shubhadip Pal's profile image
Shubhadip Pal
Raid comparison from Hitachi documentations. 

Reliability Index:
RAID6(6D+2P) > RAID6(14D+2P) >> RAID1(4D+4D) = RAID1(2D+2D) = RAID5(3D+1P) > RAID5(7D+1P)

Performance index:
RAID6(14D+2P) > RAID5(7D+1P) > RAID1(4D+4D) > RAID6(6D+2P) > RAID1(2D+2D) = RAID5(3D+1P)

Space efficiency index:
RAID5 (7D+1P) = RAID6 (14D+2P) > RAID5 (3D+1P) = RAID6 (6D+2P) > RAID1 (4D+4D) = RAID1 (2D+2D)