[Ocfs2-devel] Why ocfs2 haven't implemented "steal" for local_alloc system files?

[Sunil Mushran]

The complexity is not worth it. 2G*16 nodes is only 32G. That's rounding
error in systems that use this file system. And you are assuming that all
other nodes have all 2G in their cache. If a node runs out of space, a more
realistic scenario is that most other nodes are also close to the end.


On Thu, Aug 1, 2013 at 1:38 AM, Younger Liu <younger.liu at huawei.com> wrote:

> On 2013/8/1 15:20, Joel Becker wrote:
> > Basically, there's so little in the cache that stealing would be too
> > complex.  Really we just want to fall back to the global, and if that is
> > empty, you're near enough ENOSPC that it doesn't much matter.
> >
> > Joel
> >
> Localalloc is a mount option. When mounting an ocfs2 volume, localalloc can
> be set a larger size. For example, 2G or a larger number.
>
> In a multi-nodes cluster, all nodes mount ocfs2 volume with localalloc=2048
> for performance consideration, if a node claims space for a file, but there
> is no space in the local_alloc and global_bitmap. It would return ENOSPC.
> However, other nodes may have lots of space which have been claimed
> in local_alloc, so ENOSPC cannot reflect the actual situation.
>
> IMO, if there is no space both in the local_alloc and global_bitmap,
> it should steal space from other nodes local_alloc.
>
> Thx,
> Younger.
>
> > On Wed, Jul 31, 2013 at 08:33:48PM -0700, Sunil Mushran wrote:
> >> Because it makes no sense. Unlike inode/extent allocs, local_alloc is a
> >> temporary cache. If you fail to allocate, you fallback to the global
> bitmap.
> >>
> >>
> >> On Sat, Jul 27, 2013 at 3:27 AM, Younger Liu <younger.liu at huawei.com>
> wrote:
> >>
> >>> Hi,
> >>>   While analyzing ocfs2 block allocation, I found:
> >>>   When claiming space from inode_alloc (or extent_alloc) system files,
> >>> if there is no enough space in inode_alloc (or extent_alloc) and
> >>> global_bitmap, it could steal space from other slots.
> >>>   But when claiming space from local_alloc system files, and no
> >>> enough space in local_alloc and global_bitmap, it returns -ENOSPC.
> >>>
> >>>   Why ocfs2 haven't implemented "steal" for local_alloc system files?
> >>>   Is there any some reasons?
> >>>
> >>>
> >>> _______________________________________________
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> >>> Ocfs2-devel at oss.oracle.com
> >>> https://oss.oracle.com/mailman/listinfo/ocfs2-devel
> >>>
> >
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> >
> >
>
>
>
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