[Gluster-users] files on gluster brick that have '---------T' designation.

[Shishir Gowda]

Hi,

distribute xlator splits its namespace into smaller namespace's spread across its subvolumes(a.k.a layouts).

The hash value of a file falls under a particular layout, and that subvolume is known as the hashed subvol. When a file is created, it is created under the hashed subvol.

Over the life cycle of a file, when rename/mv operations are involved, the new hashed subvolume might end up to be different compared to existing subvolume. So, instead of moving the file, we create link files (----T 0-byte) files, with extended attributes on the new hashed subvol. The extended attributes point to the old subvolume(cached subvol) where the file data actually existed(renamed file).


A full rebalance (and sometimes with force option, if target subvols are exceeding src subvol size) will clean up these link files, but actually migrating the cached files to the correct hashed subvol.

With regards,
Shishir

----- Original Message -----
From: "s19n" <mailbox at s19n.net>
To: gluster-users at gluster.org
Sent: Tuesday, August 21, 2012 5:57:59 PM
Subject: Re: [Gluster-users] files on gluster brick that have '---------T' designation.

* Shishir Gowda <sgowda at redhat.com> [2012 08 20, 22:09]:
> These are valid files in glusterfs-dht xlator configured volumes.
> These are known as link files, which dht uses to maintain files on
> the hashed subvol, when the actual data resides in non hashed
> subvolumes(rename can lead to these).

Hello,

 since I also have noticed those files, could you please clarify (or
point me to the proper documentation) what 'hashed subvolumes' and
'non hashed subvolumes' are?

> The cleanup of these files will be taken care of by running
> rebalance.

 When you say rebalance you mean a fix-layout or a full rebalance with
data migration? Should I plan to issue a rebalance request periodically
to get rid of those files?


Thank you very much in advance for your attention,
Best regards

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