On 3/19/2010 3:25 PM, Mike Snitzer wrote: > Any reason why you'd like to use DOS partitioning (first primary > partition starting at 63rd sector)? Convention. I am looking into using GPT instead though. > Anyway, if you have a recent kernel (e.g. 2.6.33) you'll be in good > shape regardless. If you create a partition on the device (using DOS > partitions) the kernel _should_ be aware of where the partition starts > and tell you how far you'd have to shift the start of your LVM2 PV data > area to get it perfectly aligned relative to the underlying physical > block size. Check for example: > # cat /sys/block/sda/sda1/alignment_offset > > But if your device is using 512b physical_sector_size you'll just have a > 0 for alignment_offset. Check physical_block_size with: > # cat /sys/block/sda/queue/physical_block_size 0 alignment, physical block size 512. > Also verify that your SSD device is naturally aligned (aka > alignment_offset=0); I'd wager it is naturally aligned: > # cat /sys/block/sda/alignment_offset Kernel thinks so, and based on performance tests it appears so. > All said, even if you have an older kernel, to manually get what you > want (shift start to account for DOS partition at 63rd sector, align PV > pe_start on a 512K boundary), please try: > # pvcreate --dataalignmentoffset 512b --dataalignment 512K ... Won't that just add one sector to the start, placing it at sector 1025? How does an alignment offset of 1 sector account for the partition starting on sector 63? _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
