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Re: 1B files, slow file creation, only AG0 used

To: stan@xxxxxxxxxxxxxxxxx
Subject: Re: 1B files, slow file creation, only AG0 used
From: Michael Spiegle <mike@xxxxxxxxxxxxxxxx>
Date: Mon, 12 Mar 2012 15:11:25 -0700
Cc: xfs@xxxxxxxxxxx
In-reply-to: <4F5D6690.3010006@xxxxxxxxxxxxxxxxx>
References: <CAEm1Pvny7Q2rrsCLURvo5kQM3vt+yMg17WxoSYGKVWm7Lgp8MA@xxxxxxxxxxxxxx> <4F5ADFCB.9010602@xxxxxxxxxxx> <CAEm1PvmTCaw_eSNPPvQLvwu5X7ywseOBbALxMkSLnOT9iQd6fQ@xxxxxxxxxxxxxx> <4F5D6690.3010006@xxxxxxxxxxxxxxxxx>
Reply-to: mike@xxxxxxxxxxxxxxxx
On Sun, Mar 11, 2012 at 7:59 PM, Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx> wrote:
>
> When using the inode32 allocator and having 64k dirs, and seeing no
> files in AGs other than AG0, might this tend to suggest that these are
> zero length files or similar, being stored entirely within the directory
> inodes, thus occupying no extents in other AGs?  Would this tend to
> explain why 'everything' is in AG0?
>

If any of our files are 0-bytes, then that would probably be an error.
 Our files are anywhere from 1K-50KB.  There could be files outside of
that range, but they're at the edges of the bell curve.

>
> If my guess about these files is correct, mounting with inode64 and
> writing additional files should create new directory inodes in other
> AGs, but you still won't see file extents in those other AGs, just as
> you don't in the first AG.
>
> Are you using this XFS filesystem as a poor man's database or something
> similar?  This would tend to explain a billion files, with no extents,
> wholly stored in directory inodes, only in AG0, while using the inode32
> allocator.
>
> --
> Stan

I mentioned it in another reply, but we just found out that the AG
information appeared to be cached.  We had to unmount/remount the
filesystem in order to get updated counts.  We do see other AGs being
used when mounting with inode64.

No, we have a database for the database stuff =)  These are legitimate
pieces of content that we're storing for our users (many many billions
of files).  We were using EXT3, but recently moved to XFS.  It's nice
to not be constrained by statically-allocated inodes!

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