======Posted by Jon======
Can anyone provide guidance on a time-per-GB for RAID rebuild times for a P420i with 2GB cache ?
Approximate or min and max would be fine.
I need this for both 6Gb 10K SAS HDD (eg 900GB drive) for a RAID5 set and also for 12Gb 800GB SSD drives in a RAID1 set as well.
Gen8 P420i SmartArray Rebuild Times
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1. 本版是定位于惠普服务器的技术讨论区。
2. 本版鼓励发帖共同讨论技术问题，不鼓励站内信件私下交流，独知知不如众知知。
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Re: Gen8 P420i SmartArray Rebuild Times
=======Posted by Robert=======
There are several factors that affect rebuild performance.
Drive speed is the main limit.
• A HDD is limited by its rpm and bit density.
• An SSD is limited by how many flash cells the drive has in parallel. Ideally, they can saturate their interface link rate.
• Writes to SSDs are usually slower than reads from SSDs.
Other bottlenecks:
• As the RAID array gets bigger, more drives must be read to rebuild the data. 7+1 RAID-5 will outperform 15+1 RAID-5.
• Controller memory bandwidth (XOR engine). Use a 64-bit wide cache module for best results (2 GB qualifies).
• Not using all the controller phys (e.g., putting all drives behind one x4 port rather than scattering them across both x4 ports)
• Slower SAS links between the controller and drive (e.g., 12 Gb/s drive in a 6 Gb/s backplane or JBOD). The P420i is 6 Gb/s, so won't ever attain 12 Gb/s from that SSD.
Some things help rebuild performance:
• Smart Array divides the logical drive in 16 regions and only rebuilds the sections that have been written
There are several factors that affect rebuild performance.
Drive speed is the main limit.
• A HDD is limited by its rpm and bit density.
• An SSD is limited by how many flash cells the drive has in parallel. Ideally, they can saturate their interface link rate.
• Writes to SSDs are usually slower than reads from SSDs.
Other bottlenecks:
• As the RAID array gets bigger, more drives must be read to rebuild the data. 7+1 RAID-5 will outperform 15+1 RAID-5.
• Controller memory bandwidth (XOR engine). Use a 64-bit wide cache module for best results (2 GB qualifies).
• Not using all the controller phys (e.g., putting all drives behind one x4 port rather than scattering them across both x4 ports)
• Slower SAS links between the controller and drive (e.g., 12 Gb/s drive in a 6 Gb/s backplane or JBOD). The P420i is 6 Gb/s, so won't ever attain 12 Gb/s from that SSD.
Some things help rebuild performance:
• Smart Array divides the logical drive in 16 regions and only rebuilds the sections that have been written