Hi list. Am I the first to battle performance related issues from the setting of /proc/sys/vm/max-readahead? It seems there is quite a few threads floating around the net related to performance of the md driver with external disks connected over FC. But I was pretty confused because /proc/mdstat reports the bogus old device read_ahead value, and the md driver silently (well, not really) uses /sys/vm/max-readahead to calculate a window size which makes quite a difference in my setup where I have some scsi disks on a relatively high-latency SAN. Possibly this issue only shows itself when running RAID-1 where the chunksize is not used (there seem to be a bug in Jacob's howto in section 5.10 on that point) Maybe the issue only arises on RedHat because they for some reason chose to make the 31 default value of /proc/sys/vm/max-readahead in their EL3 release, where the older default of 127 is more resonable? I don't mind writing the blurb myself, if I'm not totally off course in my error diagnostics. -- Morten -- Morten Sylvest Olsen, System Developer Medical Insight A/S, Hovedgaden 451 C,2640 Hedehusene, Denmark Phone:+4546550444, Mobile:+4551573092,Mail: mso@xxxxxxxxxxxxxxxxxxx - 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
