On Dec 29, 2013, at 2:11 PM, Kai Krakow <hurikhan77+bt...@gmail.com> wrote:

> 
> * How stable is it? I've read about some csum errors lately…

Seems like bcache devs are still looking into the recent btrfs csum issues.

> 
> * I want to migrate my current storage to bcache without replaying a backup.
>  Is it possible?
> 
> * Did others already use it? What is the perceived performance for desktop
>  workloads in comparision to not using bcache?
> 
> * How well does bcache handle power outages? Btrfs does handle them very
>  well since many months.
> 
> * How well does it play with dracut as initrd? Is it as simple as telling it
>  the new device nodes or is there something complicate to configure?
> 
> * How does bcache handle a failing SSD when it starts to wear out in a few
>  years?

I think most of these questions are better suited for the bcache list. I think 
there are still many uncertainties about the behavior of SSDs during power 
failures when they aren't explicitly designed with power failure protection in 
mind. At best I'd hope for a rollback involving data loss, but hopefully not a 
corrupt file system. I'd rather lose the last minute of data supposedly written 
to the drive, than have to do a fuil restore from backup.

> 
> * Is it worth waiting for hot-relocation support in btrfs to natively use
>  a SSD as cache?

I haven't read anything about it. Don't see it listed in project ideas.

> 
> * Would you recommend going with a bigger/smaller SSD? I'm planning to use
>  only 75% of it for bcache so wear-leveling can work better, maybe use
>  another part of it for hibernation (suspend to disk).

I think that depends greatly on workload. If you're writing or reading a lot of 
disparate files, or a lot of small file random writes (mail server), I'd go 
bigger. By default sequential IO isn't cached. So I think you can get a big 
boost in responsiveness with a relatively small bcache size.


Chris Murphy--
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