X-bit labs

NVIDIA nForce4 SLI (Intel Edition) Platform Review (page 11)

Category: Chipsets

by Ilya Gavrichenkov

[ 04/13/2005 | 07:07 PM ]

Since we came to speak about RAID arrays, it is important to stress that nForce4 SLI (Intel Edition) supports RAID 5 array type, which wasn’t supported by the nForce4 solution for Athlon 64 systems. These arrays allow recovering data in case one of the HDDs fails, because the data is not just split between a few hard drives: there is some additional info stored in this type of array. In case of a RAID 5 array of three HDDs there is always the third data block formed by the first two XOR operations and containing the parity information. The data blocks with the parity information are “spread” all over the drives, so that all three members of the RAID 5 array could be loaded evenly.

RAID 5 arrays are positioned as an alternative solution to RAID 0+1, and it can be built with fewer hard disk drives. Theoretically, RAID 5 ensures higher data security and disk subsystem performance with lower losses of storage space. Fair enough, as in a RAID 5 array of three HDDs the actual data storage space equals 2/3 of the overall capacity of all three drives.

Anyway, quality RAID 5 implementation requires additional computational resources. For example, professional controllers supporting RAID 5 feature a special RISC processor performing XOR calculations in real time. That is why it was extremely interesting to find out the actual performance of the RAID 5 arrays supported by the chipset Serial ATA controllers. For our experiments we created a RAID 5 array of three Western Digital Raptor WD740GD hard disk drives. The obtained results are given below:

Frankly speaking the results are quite puzzling. RAID 5 arrays created by the chipset controllers turned out extremely slow.

When we measured the linear read and write speeds, the situation got a little bit clearer. The problem with RAID 5 support in the modern chipset is connected with dramatically low data write speed, which is limited by the real time XOR calculations for this data.

This way, you may be interested in RAID 5 arrays supported by nForce4 SLI (Intel Edition) chipset as well as by i955X chipset only if you are trying to save some disk space and do not care that much about the fast performance of this array. So, RAID 1 and RAID 0+1 arrays will definitely remain very popular, even though now the chipset will also be offering RAID 5 support.