grub: LVM cache booting
5.3 Booting from LVM cache logical volume
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The LVM cache logical volume is the logical volume consisting of the
original and the cache pool logical volume. The original is usually on
a larger and slower storage device while the cache pool is on a smaller
and faster one. The performance of the original volume can be improved
by storing the frequently used data on the cache pool to utilize the
greater performance of faster device.
GRUB boots from LVM cache logical volume merely by reading it's
original logical volume so that dirty data in cache pool volume is
disregarded. This is not a problem for "writethrough" cache mode as it
ensures that any data written will be stored both on the cache and the
origin LV. For the other cache mode "writeback", which delays writing
from the cache pool back to the origin LV to boost performance, GRUB may
fail to boot in the wake of accidental power outage due to it's
inability to assemble the cache device for reading the required dirty
data left behind. The situation will be improved after adding full
support to the LVM cache logical volume in the future.
Info Catalog
grub: Loopback booting
grub: Booting
grub: OS-specific notes