[linux-lvm] cache on SSD makes system unresponsive

[matthew patton]

>  But if it's something that only exhibits in writeback mode rather than writethrough, then I'd guess it's to do with the
> list of writeback work that the policy builds.  So check

OP is being coy about the DD command but I saw it mentioned off-hand earlier.

dd if=/250GB_file/on_LVM/H800_vdev of=/dev/null

It's a pure, streaming read. LVM cache should be doing absolutely nothing.