Alignment ensures optimal use of your drive, sometimes software gets this wrong
and compensates by using a larger cache, check
cat /sys/block/sd?/queue/optimal_io_size
to correct that you have to re format (likely both the GPT/LVM layers) look
into --dataalignment and --dataalignmentoffset of pvcreate
shareimprove this answer
edited Jun 8 '17 at 7:26
answered Jun 8 '17 at 7:18
user1133275
1,932412
• $ cat /sys/block/sdb/queue/optimal_io_size 33553920 33MB for a 2TB
USB HDD? 268431360 for a 4TB??? – Tom Hale Jun 10 '17 at 5:17
• @Tom they both should drop to 0 if you fix the alignment –
user1133275 Jun 11 '17 at 10:38
• I'm seeing this, but realised that 33553920 / 512 = 65535. Is it
possible something's reporting "-1" as optimal IO size in sectors? – Steve Dee
Mar 18 at 11:33
