DRBD 9 Now Supports Fencing In Pacemaker

Fencing is the process of isolating a node from a computer cluster or protecting shared resources when a node appears to be malfunctioning. As the number of nodes in a cluster increases, so does the likelihood of failure.1

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“umount is too slow”

A question we see over and over again is

Why is umount so slow? Why does it take so long?

Part of the answer was already given in an earlier blog post; here’s some more explanation. Read more

“read-balancing” with 8.4.1+

DRBD 8.4.1 introduces a new feature: read-balancing, which is configured in the disk section of the configuration file(s). This feature enables DRBD to balance read requests between the Primary/Secondary nodes. Read more

Make the kernel start write-out earlier

Similar to the recent post about setting the vm.min_free_kbytes value there’s another sysctl that might improve the behaviour: the dirty ratio. Read more

Increase vm.min_free_kbytes for better OOM resistance

Depending on your setup and your workload (eg. within a virtual machine with little memory and much I/O) you could get into the situation that the kernel has little memory left, so wants to write some dirty pages to disk, but cannot, because for that it would need some memory free! Read more