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List:       linux-xfs
Subject:    Need xfs Assistance With Weird Problem
From:       Larry K <lunchtimelarry () gmail ! com>
Date:       2005-09-29 1:02:51
Message-ID: 61f78fbe05092818029050dfb () mail ! gmail ! com
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I have a FC3 box running mythtv.

Up until recently, I had been running LVM (and xfs) with only a single
physical volume of 300GB. I probably have 100GB of data files in the volume,
waiting to be watched. So, Myth was running fine and all was well, except I
had another 150GB partition just laying around, not in use. So, I decided to
extend my volume group and add this 150GB to make it a total of 450GB, like
so:

   1. Using fdisk, deleted /dev/hda4 partition
   2. Using fdisk, created /dev/hda4 as LVM
   3. Created physical volume: pvcreate /dev/hda4
   4. Extended volume group: vgextend vg /dev/hda4
   5. Ran vgdisplay to see amount of free space that needs to be extended
   (18214)
   6. unmount the volume group: umount /dev/vg/video
   7. extend: lvextend -l +18214 /dev/vg/video
   8. mount /dev/vg/video
   9. grow the xfs file system: xfs_grow /dev/vg/video
   10. Remove /video from /etc/fstab

Now, df -k shows the new space:

[root@mythtv ~]# df -k
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/hda2 10080520 2938120 6630332 31% /
/dev/hda1 101086 16752 79115 18% /boot
none 257908 0 257908 0% /dev/shm
/dev/mapper/vg-video 442105856 113816336 328289520 26% /video2

Everything appeared to be OK. I now had a 450GB partition instead of 300GB.
However, I soon discovered that new files are written with a length of zero
(empty files). Doh! The mythfrontend was able to play back the existing
files that were in the VG, but if I tried to delete a file, the app would
hang. That's when I knew I had a problem for sure.

Also odd is that when, as root, I cat /dev/video0 > /video2/xxx.mpg, this
file is also empty. However, if I copy an existing file, as in

cp /video2/blah blah.nuv /video2/xxx, it shows up with the proper length. So
old files copy correctly, but new files are not written correctly.

There are no error messages in either the mythtv application logs, nor the
log file at /var/log/messages.

I did notice that one of the HDs is running DMA 100, while the other is DMA
133. Does this matter to xfs or even to LVM?

Anyone have any thoughts as to what might be causing this? Diagnostics?
Hidden error messages?

Backing up 100GB of data is gonna be difficult. About the only way I have is
to ftp the data to another box, which will take at least 24 hours, according
to my estimates.

Since everything was working before I expanded the file system from 300GB up
to 450GB, I suppose going back might be an option. Since there is no way to
shrink an xfs file system, I'm not sure if I can go back now?

Thanks!


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