Re: [PATCH 00/15] btrfs: Hot spare and Auto replace

[Anand Jain <anand.jain@oracle.com>]

Thanks for commenting.

>>> I'm sorry but I didn't quite see the benefit of a spare device.
>> Aside from what Duncan said (and I happen to agree with him), there is
>> also the fact that hot-spares are (at least traditionally in most RAID
>> systems) usually used with RAID5 or RAID6 (or some other parity scheme).
>>
>> So, to summarize:
>> 1. Hot spares are more useful for most users in global context, and in
>> that case only if they have more than one filesystem.
>> 2. A pool of hot spares is even more useful.
>
> Agreed, just as Ducan said.
> Although only one spare device is supported yet.

  You can add more than one spare device currently.

>> 3. Assuming whole disk usage (as opposed to partitioning), the hot spare
>> will have no load on it until it gets used, at which point it will
>> almost always be in better physical condition than the device it
>> replaced (which is important for HA systems, in such cases you replace
>> the disk that failed, and make the new disk a hot spare)
>
> OK, that's also right, if no one is calling btrfs dev scan with a interval.

   Not too sure what you mean about the scan part.

Thanks, Anand