Rustedt, Florian wrote:
Hello List, If the speed on RAID 0 is based on reading out in parallel, then it must be the same on RAID 1, mustn't it? On RAID 1, it is possible, to read two blocks in parallel to speed up, too. I tried to measure this some weeks ago, but i couldn't get over the read-performance of a single disk on my raid 1, so that means, that the software-raid does not use this easy possibility to speed up?
We've had this discussion before, and the RAID code does not take advantage of running reads in parallel to satisfy readahead or anything else. I seen it said that this is on a per-thread basis, but a simple test suggests that it's on a process basis, setting two threads to read alternating 10k blocks as fast as possible ran no faster than a single thread. However, running against RAID-10, even a single thread seemed to run far faster than the speed of a single drive.
Lightly tested, don't take this as the last word. -- bill davidsen <davidsen@xxxxxxx> CTO TMR Associates, Inc Doing interesting things with small computers since 1979 - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
