On Fri, Jun 15, 2007 at 04:36:07PM -0400, Justin Piszcz wrote: > Hi, > > I was wondering if the XFS folks can recommend any optimizations for high > speed disk arrays using RAID5? [sysctls snipped] None of those options will make much difference to performance. mkfs parameters are the big ticket item here.... > There is also vm/dirty tunable in /proc. That changes benchmark times by starting writeback earlier, but doesn't affect actual writeback speed. > I was wondering what are some things to tune for speed? I've already > tuned the MD layer but is there anything with XFS I can also tune? > > echo "Setting read-ahead to 64MB for /dev/md3" > blockdev --setra 65536 /dev/md3 Why so large? That's likely to cause readahead thrashing problems under low memory.... > echo "Setting stripe_cache_size to 16MB for /dev/md3" > echo 16384 > /sys/block/md3/md/stripe_cache_size > > (also set max_sectors_kb) to 128K (chunk size) and disable NCQ Why do that? You want XFS to issue large I/Os and the block layer to split them across all the disks. i.e. you are preventing full stripe writes from occurring by doing that. Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group - 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
