Why does it take so darn long to build a RAID5 array

[Pray To Jesus]

RAID 5

4 disk 2TB each

 

[Pray To Jesus]

Initializing (Background) 15%
remaining time:07:47:51

 

[Mark R]

It takes about 8 hours to read/write a 2TB hard drive. That is the limiting factor, and one of the reasons why RAID5 is inappropriate for 2TB + drives.

 

[imagoon]

It varies heavily on the RAID and disk controllers also. From those numbers I roughly estimate that you are only initializing at around 50-60MB/s.

 

[corkyg]

The bigger the drive, the longer the time.

 

[BrightCandle]

Raid 5 to rebuild has to go through every byte on all of the disks and calculate an XOR and store write out that parity information to one of the disks. In your case 3 disks are being read and then the forth is being written to with parity data. 2TB at 50MB/s or (true sustained performance considering the calculation being done on the CPU) takes a long time.

 

[Pray To Jesus]

Yea RAID 5 was a turtle so I switched the array into a RAID10.

 

[yinan]

Get a controller that can do the initialization in the background.

 

[Gunbuster]

A lot is down to the RAID card. I have a Dell PERC H700 that initialized a RAID5 set of 7 4TB drives in around 5 Hours.

 

[exdeath]

Disk IO and bandwith sucks.

 

[Zxian]

A lot is down to the RAID card. I have a Dell PERC H700 that initialized a RAID5 set of 7 4TB drives in around 5 Hours.

My 3ware 9650SE-8LPML initialized my eight 3TB drives in RAID6 in about 10 hours. Don't do traditional RAID5 unless you're on a proper hardware controller. Forget about even thinking of doing it with your onboard SATA controller.