Re: ENOSPC on heterogeneous raid 0

[sensille <sensille@gmx.net>]

cwillu wrote:
> On Sun, Dec 12, 2010 at 8:24 AM, Hubert Kario <hka@qbs.com.pl> wrote:
>> On Wednesday 08 of December 2010 22:53:25 William Sheffler wrote:
>>> Hello btrfs community.
>>>
>>> First off, thanks for all your hard work... I have been following
>>> btrfs with interest for several years now and very much look forward
>>> to the day it replaces ext4. The real killer feature (of btrfs
>>> specifically) for me is the ability to add *and remove* devices from a
>>> filesystem, as this allows rolling upgrades of my server's disks. I
>>> have a 16 port 3ware 1650SE on which I have a number of small raid
>>> units and it will be fantastic to be able to remove the oldest,
>>> upgrade, and add the new storage back. I had previously been using
>>> ZFS, but since ZFS doesn't allow removal of devices, this rolling
>>> upgrade strategy doesn't work.
>>>
>>> My question is this: can btrfs handle striping (raid 0) across
>>> heterogeneous devices? I seem to be losing any capacity on the larger
>>> disk beyond what is available on the smaller disk. I really hope there
>>> is some simple fix!
>> Yes, it can handle stripping over devices of different size, unfortunately
>> you're still limited to <size of smallest device>*<number of devices>
>>
>> if you want to use all the available space use "-d single" when creating
>> volume
>>
>> for details, read the recent thread "800GB free, but no space left"
> 
> If I'm not mistaken, -d single doesn't mean anything yet on a
> multi-device system:  you'll still get raid0.

I don't think so. -d single does what it is expected to do. Also my recent
patch makes allocation on multi-device setups much better, although it is
not the last word on it.