In DRBD 8.4, several drbd.conf
default values have been updated to
match improvements in the Linux kernel and available server hardware.
al-extents
' previous default of 127 has changed to 1237, allowing
for better performance by reducing the amount of metadata disk write
operations. The associated extended resynchronization time after a
primary node crash, which this change introduces, is marginal given
the ubiquity of Gigabit Ethernet and higher-bandwidth replication
links.
Run-length encoding (RLE) for bitmap transfers is enabled by default
in DRBD 8.4; the default for the use-rle
option is yes
. RLE
greatly reduces the amount of data transferred during the
quick-sync bitmap exchange (which occurs any
time two disconnected nodes reconnect).
DRBD 8.4 defaults to masking I/O errors, which
replaces the earlier behavior of passing them on
to upper layers in the I/O stack. This means that a DRBD volume
operating on a faulty drive automatically switches to the Diskless
disk state and continues to serve data from its peer node.
Variable-rate synchronization is on by default in DRBD 8.4. The default settings are equivalent to the following configuration options:
DRBD 8.4 default options for variable-rate synchronization.
resource test { disk { c-plan-ahead 20; c-fill-target 50k; c-min-rate 250k; } ...