Re: Feature request: true RAID-1 mode

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Could you have a mode, though, where M = N at all times, so a user doesn't end up adding a new drive and get a nasty surprise?

Chris Mason <chris.mason@xxxxxxxxxxxx> wrote:

>On Wed, Jun 20, 2012 at 06:35:30PM -0600, Marios Titas wrote:
>> On Wed, Jun 20, 2012 at 12:27 PM, H. Peter Anvin <hpa@xxxxxxxxx>
>wrote:
>> > Yet another boot loader support request.
>> >
>> > Right now btrfs' definition of "RAID-1" with more than two devices
>is a
>> > bit unorthodox: it stores on any two drives.  "True RAID-1" would
>> > instead store N copies on each of N devices, the same way an actual
>> > RAID-1 would operate with an arbitrary number of devices.
>> >
>> > This means that a bootloader can consider a single device in
>isolation:
>> > if the firmware gives access only to a single device, it can be
>booted.
>> >  Since /boot is usually a very small amount of data, this is a very
>> > reasonable tradeoff.
>> 
>> +1
>> 
>> In fact, the current RAID-1 should not have been called RAID-1 at
>all,
>> it is confusing.
>
>With the raid5/6 code, I'm changing raid1 (and raid10) to have a
>configurable number of copies.  So, you'll be able to have N copies on
>M
>drives, where N <= M.
>
>-chris

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