Intel chipset = hardware raid ??

ShePearl

ShePearl

Limp Gawd
Joined
Apr 16, 2004
Messages
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All those Intel chipsets for Sandy Bridge (and Ivy Bridge) such as P67, Z68 and Z77 support RAID out of the box. Can they be considered as a *hardware* RAID, or are they *software* RAID ?
 
ShePearl said:
All those Intel chipsets for Sandy Bridge (and Ivy Bridge) such as P67, Z68 and Z77 support RAID out of the box. Can they be considered as a *hardware* RAID, or are they *software* RAID ?
Click to expand...

Well, in actuality all RAID is software in one way or another, but generally it is accepted that "Hardware" RAID is that which includes seperate logic hardware which offloads the parity calculations and other overhead off the main CPU(s).
 
ShePearl said:
All those Intel chipsets for Sandy Bridge (and Ivy Bridge) such as P67, Z68 and Z77 support RAID out of the box. Can they be considered as a *hardware* RAID, or are they *software* RAID ?
Click to expand...

I consider these hardware raid for RAID 0, 1 or 10. For raid 5 these lack a battery backed cache (or an even an effective cache) and perform poorly at writes as a result.
 
Ok. Thanks.

Another related question. For those Intel chipsets (P67 / H67 / Z68 / Z77 / H77), is CPU actually controlling RAID or is it those chipset controlling RAID ?

I ask because I get conflicting results from my googling.
1. RAID is controlled by those motherboard chipset. or
2. RAID is actually controlled by CPU not chipset. Hence using RAID actually results in CPU overhead.

Which one is correct ?
 
ShePearl said:
Ok. Thanks.

Another related question. For those Intel chipsets (P67 / H67 / Z68 / Z77 / H77), is CPU actually controlling RAID or is it those chipset controlling RAID ?

I ask because I get conflicting results from my googling.
1. RAID is controlled by those motherboard chipset. or
2. RAID is actually controlled by CPU not chipset. Hence using RAID actually results in CPU overhead.

Which one is correct ?
Click to expand...

Well, it could be both actually. Depending on the CPU and chipset, it could also depend on how your board connects its drives. The different CPUs and chipsets handle differing numbers of PCIe channels, some are handled on chip, some are handled by the express chipset and some could be handled by other bridge or logic. A lot depends on which ports you actually connect to, and how those interfaces are connected to the processor. If connected to the chipset controller SATA ports, RAID0, 1 & 10 there is negligible overhead on the main CPU. That is not the case for RAID5, where there can be a significant hit to the system performance depending on a lot of variables.
 
RAID5 will require the CPU for any motherboard raid. Although that is not really the big problem (having used software raid 5/6 for over a decade at work). The CPU usage due to the XOR operation for a good software raid implementation (unless you are rebuilding or reshaping) will be less than 10% of a single core on a modern 64 bit processor. I have not seen more than that in a many years and I have over 100 drives in software raid6. The problem with motherboard raid and other windows software raid is all in the cache or the lack of an effective write behind cache causing a lot of read - calculate parity - write cycles when if the cache had the stripe available or waited to write back it would not need to read as much before writing partial stripes.

For RAID0, 1, 10 the CPU will not have to calculate parity .. so not much work although depending on the implementation may need to individually transfer data to more than 1 drive at a time where HW raid it can transfer the data to the raid controller and the raid controller will offload that to an IO CPU to handle the distribution to multiple disks at once.
 
It's FakeRAID, aka motherboard RAID, aka firmware RAID.
It's not hardware RAID nor is it software RAID, those are entirely different.
 
ShePearl said:
Ok. Thanks.

Another related question. For those Intel chipsets (P67 / H67 / Z68 / Z77 / H77), is CPU actually controlling RAID or is it those chipset controlling RAID ?

I ask because I get conflicting results from my googling.
1. RAID is controlled by those motherboard chipset. or
2. RAID is actually controlled by CPU not chipset. Hence using RAID actually results in CPU overhead.

Which one is correct ?
Click to expand...

The CPU is handling all of the calculations via the FakeRAID driver.
All the chipset does is "trick" the OS into thinking the drives are a single drive/device, but again, the CPU is doing all of the work.

Almost every variant of a motherboard RAID controller will do this with a few rare exceptions.
 
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