Question marks

Here is how to clear question marks in ls -l following a disk crash

1. To free pagecache

echo 1 > /proc/sys/vm/drop_caches

1. To free dentries and inodes

echo 2 > /proc/sys/vm/drop_caches

1. To free pagecache, dentries and inodes

echo 3 > /proc/sys/vm/drop_caches

$ sudo -i
# echo 1 > /proc/sys/vm/drop_caches

... wait ... try

ls /nfs/scratch/A/xyz/protomer/I.. still didn't work

..wait ... try

ls /nfs/scratch/A/xyz/protomer/I 

again, worked

and this

lvscan
pvscan
vgchange -a y 
mount -t ext4 /dev/vg_system/lv_root /mnt/resh5

finally, reboot gimel if nothing else works.