Hi all, some time ago I was reporting about a strange issue. I have a two HDDs system, with a small RAID1 (/boot) and the rest as RAID10 f2 (with LVM on top). It seems that /dev/sdb has more reads than /dev/sda. I had a quick check, with "iostat", and it seems that all small reads, somehow below 1~4KiB, are done from /dev/sdb2, regardless. Actually, it seems that only if there is a pending (small) read, this will be scheduled to /dev/sda2, but non-overlapping small reads seem to happen always from /dev/sdb2. This occurs with the RAID10, but it seems also with the RAID1. In normal operation, this does not seem to lead to problems, but during the smart long test /dev/sdb takes by far more time than /dev/sda, since each small read stop the test, and small read occurs whenever there is a small write from syslog or similar. Note that failing and removing /dev/sdb2 results in much shorter time for the smart test, about 1hr30min vs. the 6~7hrs with the drive still attached to RAID10. Is there any way to tune which is the "preferred" drive or the "preferred" policy in case of these small (or big) reads? Could this be due to HW configuration? The two HDDs are numbered SATA1 and SATA2 in BIOS, there are still SATA3 and SATA4 ports somehow available (SATA3 has a DVD). How are the reads scheduled withing the RAID10 software? Thanks, bye, -- piergiorgio -- 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
