On 03/02/2013 04:15 AM, Stan Hoeppner wrote: > On 3/1/2013 10:06 AM, Adam Goryachev wrote: >> 15) "Make sure all LVs are aligned to the underlying md device geometry. >> This will eliminate any possible alignment issues." >> What does this mean? The drive partitions are now aligned properly, but >> how does LVM allocate the blocks for each LV, and how do I ensure it >> does so optimally? How do I even check this? > > I'm not an LVM user so I can't give you command lines. But what I can > tell you follows, and it is somewhat critical to RMW performance, more > for rust but also for SSD to a lesser degree. Run "dmsetup table" and look at the start sectors for your volumes: > Fast-Root: 0 314572800 linear 9:3 3072 This volume starts at sector 3072 (1.5MB) on /dev/sda3. So the volume alignment within LVM is 512K. >> Is it worth reducing the chunk size from 64k down to 16k or even smaller? > > 64KB chunks should be fine here. Any gains with a smaller chunk would > be small, and would pale in comparison to the amount of PITA required to > redo the array and everything currently sitting atop it. Remember you'd > have to destroy it and start over. You can't change chunk size of an > existing array. Actually, you can. For levels 0 and 4,5,6. HTH, Phil -- 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
