On Wed, 25 Sep 2002, Adam Radford wrote: > This is because of the vmlayer and your bdflush settings and the fact > that you are running a journalling filesystem. Our raid 5 caching > strategy gives the best results when given sequential writes. Doing > journaling fs and caching writes in the vmlayer causes the firmware > caching strategy to perform 'sub optimal' since the lba's accessed > aren't actually sequential. Thus your 15 MB/s. We do do elevator seek > in the FW, but this can only help you so much. Any specifics in the bdflush settings I should be aiming for? I have fiddeled some with the settings and I cannot seem to make much of a difference. Would it help to mount that particular partition in with "sync" mount option? I have already changed the mount option to data=writeback in order to have less journaling data being thrown around. What I also do not understand is that in some 5 second intervals I get iostat claiming there was only 500 kilobyte/s written when doing my test with dd if=/dev/zero of=testfile bs=1024000 count=2000. What in the world could cause the vm layer to have that big of an impact that it would only be able to write just 500 kilobytes in a second? I have this bdflush setting at the moment: echo 100 5000 640 2560 150 30000 5000 1884 2 > /proc/sys/vm/bdflush I have made several radical changes to the bdflush settings and if any, it made things worse. -- Mikael Abrahamsson email: swmike@swm.pp.se - 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
