Re:BCache Gets New Maintainer, NVMe Improvements and More fo...
by rogerbinns on Wednesday November 15, 2017 @10:49AM
(#15704539)
TLDR: I do not recommend using bcache with btrfs, but this is a sample of 1.
I've been using bcache (SSD) with btrfs (4TB hard drive) for while, and am in the process of ripping it out. What I found is the filesystem gets wedged if there is a heavy write load (lots of files) such as running debootstrap. This happened with both write-through and write-back. The symptoms are all requests stall and a kernel log message about hung btrfs tasks. Only a reboot (typically needing sysrq keys to complete) works.
The problem did not occur previously when using btrfs without bcache and the same workload. It also doesn't occur during "lighter" workloads.
I've been using bcache (SSD) with btrfs (4TB hard drive) for while, and am in the process of ripping it out. What I found is the filesystem gets wedged if there is a heavy write load (lots of files) such as running debootstrap. This happened with both write-through and write-back. The symptoms are all requests stall and a kernel log message about hung btrfs tasks. Only a reboot (typically needing sysrq keys to complete) works.
The problem did not occur previously when using btrfs without bcache and the same workload. It also doesn't occur during "lighter" workloads.