Hi,
I'm using Oracle Linux 7.3. with NetApp LUNs and multipathing.
The NetApp LUNS has a block size of 4096, so the "max_sectors_kb" in OS has to set to 4096, too.
If you use parted to check disk alignment or other things there is a major bug:
Important parameter "max_sectors_kb" is reset to 64 if you run and quit the parted program:
#cat /sys/class/block/sda/queue/max_sectors_kb
4096
# parted
GNU Parted 3.1
Verwende /dev/sda
Willkommen zu GNU Parted! Geben Sie 'help' ein, um eine Liste der verfügbaren Kommados zu erhalten.
(parted) quit
# cat /sys/class/block/sda/queue/max_sectors_kb
64
The reset of this value causes many errors like this:
kernel: blk_cloned_rq_check_limits: over max size limit.
Then you wil get flapping multipaths and the instance will crash, only resolvable by reboot!
Its become more important, because the orachk uses parted to test disks. During runing orachk the issue is occured in my env.
UPDATE:
Found this on Red Hat
https://access.redhat.com/solutions/43861
Have to add an udev rule:
#vi /etc/udev/rules.d/71-block-max-sectors.rules
ACTION=="add|change", SUBSYSTEM=="block", ENV{ID_VENDOR}=="NETAPP", RUN+="/bin/sh -c '/bin/echo 4096 >> /sys%p/queue/max_sectors_kb'"
Now it seems to work!
Could somebody inform the Oracle Linux devteam. I have no contact for doing so, thank you.
Regards Peter