> From: tech-boun...@lopsa.org [mailto:tech-boun...@lopsa.org] On Behalf > Of Doug Hughes > > RAID-5/6 are bad at IOPS. You get the equivalent IOPS of one disk > (because all disks have to ask in synchronicity. But, for throughput, > they are just fine. As long as you're writing more than (and preferably > in multiples of) the stripe width, there's no penalty with a modern > processor. zoom zoom for large sequential throughput.
I find this a gray area. Below are the results of benchmarks I did in November. As you can see, my raid5 which should perform like 4 disks ... performed like 3.5 for reads, and 2.2 for writes. While that is an awful lot of overhead, the raid5 & 6 were actually better for sequential operations than the equivalent raid-10 setup. Conclusion: raid-10 is better for random ops, while raid5/6 is better for sequential ops. 1 disk: 1.0 read G/s sustained 1.0 write G/s sustained 2-disk mirror: 1.7 read G/s sustained 1.0 write G/s sustained 3-disk mirror: 2.5 read G/s sustained 1.0 write G/s sustained 2 mirrors striped: 3.3 read G/s sustained 1.5 write G/s sustained 3 mirrors striped: 5.4 read G/s sustained 1.5 write G/s sustained raid5 (5 disks capacity of 4) 3.5 read G/s sustained 2.2 write G/s sustained raid6 (6 disks capacity of 4) 3.4 read G/s sustained 1.9 write G/s sustained _______________________________________________ Tech mailing list Tech@lopsa.org http://lopsa.org/cgi-bin/mailman/listinfo/tech This list provided by the League of Professional System Administrators http://lopsa.org/
