On 2016-05-04 19:18, Dmitry Katsubo wrote:
Dear btrfs community,
I am interested in spare volumes and hot auto-replacement feature [1]. I have a couple of questions:
* Which kernel version this feature will be included?
Probably 4.7. I would not suggest using it in production for at least a
few cycles though (probably 4.9).
* The description says that replacement happens automatically when there is any write failed or flush failed. Is it possible to control the ratio / number of such failures? (e.g. in case it was one-time accidental failure)
As far as I know, no, it just happens.
* What happens if spare device is smaller then the (failing) device to be replaced?
I'm pretty sure that it doesn't get replaced.
* What happens if during the replacement the spare device fails (write error)?
I'm not certain about this one.
* Is it possible for root to be notified in case if drive replacement (successful or unsuccessful) took place? Actually this question is actual for me for overall write/flush failures on btrfs volume (btrfs monitor).
There isn't any built-in monitoring in BTRFS that I know of, there are a
couple of options though for monitoring. The simplest and probably most
reliable is to write a script to poll for changes in the error counts.
You can also check the filesystem mount options (without the hot-spare
functionality, if there's an error, the filesystem will (usually) get
remounted read-only, and this also works for most other filesystems too).
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