Re: [Gluster-devel] cluster/stripe on tmpfs

[Angel]

from man 5 ttr

derived from lecture of 
http://acl.bestbits.at/pipermail/acl-devel/2007-May/002034.html
:

EXTENDED ATTRIBUTE NAMESPACES
       Attribute names are zero-terminated strings.  The attribute name is 
always specified in the fully qualified  namespace.attribute
       form, eg.  user.mime_type, trusted.md5sum, system.posix_acl_access, or 
security.selinux.

       The  namespace  mechanism is used to define different classes of 
extended attributes.  These different classes exist for several
       reasons, e.g. the permissions and capabilities required for manipulating 
extended attributes of  one  namespace  may  differ  to
       another.

       Currently  the security, system, trusted, and user extended attribute 
classes are defined as described below. Additional classes
       may be added in the future.

   Extended security attributes
       The security attribute namespace is used by kernel security modules, 
such as Security Enhanced Linux.   Read  and  write  access
       permissions to security attributes depend on the policy implemented for 
each security attribute by the security module.  When no
       security module is loaded, all processes have read access to extended 
security attributes, and write access is limited  to  pro-
       cesses that have the CAP_SYS_ADMIN capability.

   Extended system attributes
       Extended  system  attributes are used by the kernel to store system 
objects such as Access Control Lists and Capabilities.  Read
       and write access permissions to system attributes depend on the policy 
implemented for  each  system  attribute  implemented  by
       filesystems in the kernel.

   Trusted extended attributes
       Trusted  extended attributes are visible and accessible only to 
processes that have the CAP_SYS_ADMIN capability (the super user
       usually has this capability).  Attributes in this class are used to 
implement mechanisms in user space (i.e., outside  the  ker-
       nel) which keep information in extended attributes to which ordinary 
processes should not have access.

   Extended user attributes
       Extended  user attributes may be assigned to files and directories for 
storing arbitrary additional information such as the mime
       type, character set or encoding of a file. The access permissions for 
user attributes are defined by the file permission bits.

       The file permission bits of regular files and directories are 
interpreted differently from the file permission bits  of  special
       files and symbolic links. For regular files and directories the file 
permission bits define access to the file's contents, while
       for device special files they define access to the device described by 
the special file.  The file permissions of symbolic links
       are  not used in access checks. These differences would allow users to 
consume filesystem resources in a way not controllable by
       disk quotas for group or world writable special files and directories.

       For this reason, extended user attributes are only allowed for regular 
files  and  directories,  and  access  to  extended  user
       attributes  is  restricted  to the owner and to users with appropriate 
capabilities for directories with the sticky bit set (see
       the chmod(1) manual page for an explanation of Sticky Directories).


El Martes, 22 de Enero de 2008 Nathan Dauchy escribió:
> Greetings,
> 
> I am trying to get the Gluster "cluster/stripe" translator to work with
> a "storage/posix" directory on a tmpfs file system.  Although
> "cluster/unify" works, it presents a limit to file sizes which may be
> created that I was hoping to avoid with striping.
> 
> The documentation here:
> http://www.gluster.org/docs/index.php/GlusterFS_Translators_v1.3#Stripe_Translator
> indicates that "Stripe needs extended attribute support in the
> underlying FS".
> 
> From what I have been able to find, "recent" kernels have extended
> attributes enabled when tmpfs is enabled.  However, I get the following
> error when trying to create a file (directory creation is fine):
> 
> # df -hP /tmp/scratch
> Filesystem            Size  Used Avail Use% Mounted on
> glusterfs              12G   24K   12G   1% /tmp/scratch
> 
> # touch /tmp/scratch/foo
> touch: cannot touch `/tmp/scratch/foo': Operation not supported
> 
> From this posting, it looks like there is also a "USER extended
> attributes" which might be needed in order to make striping work on a
> tmpfs filesystem:
> http://acl.bestbits.at/pipermail/acl-devel/2007-April/002031.html
> 
> 
> Can someone please clarify the difference between extended attributes
> and user extended attributes?
> 
> Has anyone successfully gotten "cluster/stripe" working on a tmpfs file
> system?
> 
> Does anyone have a lab setup where they could try the above patch and
> gluster on tmpfs?  (If it works, I think it would be worth pushing the
> patch into the main kernel.org tree.)
> 
> Might there be something else wrong that is preventing striping from
> working?  Or a workaround to get striping working on filesystems without
> extended attributes?
> 
> 
> I am using fuse-2.7.2glfs8, glusterfs-1.3.7, and linux-2.6.20.20.
> 
> Thanks,
> Nathan
> 
> 
> 
> 
> _______________________________________________
> Gluster-devel mailing list
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> 



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