3tcdgwg3 wrote: > Did I do anything wrong? > > I didn't see RAID 1 hits multiple drives concurrently, specially for > reading. > > I set up RAID 5, RAID 1 and single disk partitions on x86 machine, > kernel 2.4-18. > > For 800 MB breading, RAID 5 take 2/3 of time used by single disk, > but RAID 1 take 1.1 of time used by single disk. Doing anything (reading or writing) with RAID 1 set will always be slower than with a single drive. Because even with reading, you're still updating the atime on both drives. As a test, mount that partition with noatime and see if RAID-1 reading test nears to 1. Here's a nice message from while back: http://www.cs.helsinki.fi/linux/linux-kernel/2002-17/0313.html <snip> Jaime Medrano wrote: > I have taken a look at the read balancing code at raid1.c and I have found > that when a sequential read happens no balancing is done, and so all the > reading is done from only one of the mirrors while the others are iddle <snip> So RAID-1 sets don't stripe read. RAID 5 is forced to stripe seek because of its very nature of having XORed data across the drives. -eric wood - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
