Chan Chung Hang Christopher wrote: > >> We were talking about RAID1; RAID5/6 is a different area. Linux software >> RAID1 is a safeguard against disk failure; it's not designed for speed >> increase. There is a number of things that could be improved in Linux >> software RAID; read performance of RAID1 is one of them - this _is_ why >> some hardware RAID1 adapters indeed are faster than software. >> Read http://kernelnewbies.org/KernelProjects/Raid1ReadBalancing - since >> the 2.6.25 kernel a simple alternating read is implemented, but that >> does not take the access pattern into account. >> > I have not read that yet but that is odd since I have been blasted by > others before for doubting md raid1 doing multiple disk reads. I know current centos alternates because I had a box with bad memory corrupt a raid1 filesystem and after fixing it and fsck'ing the disk, errors would slowly re-appear as they were hit on the alternate disk that previous fsck runs had not seen. To really speed things up, you would want to try to avoid seeks. A simple alternating pattern may let the heads be in different places on small reads, but for a large file you will end up doing the same head motions on both drives (wasting the same time) as the reads alternate. -- Les Mikesell lesmikesell at gmail.com