Writing to an NFS share truncates files on >8Tb Raid + LVM2

[Ramon van Alteren <ramon@vanalteren.nl>]

Hi All,

I'd like to report a situation which looks like a bug in the kernelbased
nfs server implementation.

I've recently build a 9Tb NAS for our serverpark out of 24 SATA disks
& 2 3ware 9550SX controllers. The storage is exported using nfs version
3 to our servers. Writing onto the local filesystem on the NAS works
fine, copying over the network with scp/nc etc. works fine as well.

However writing to a mounted nfs-share at a different machine
truncates files at random sizes which appear to be multiples of 16K.
I can reproduce the same behaviour with a nfs-share mounted via the
loopback interface.

Following is output from a test-case:

On the server in /etc/exports:
/data/tools     10.10.0.0/24(rw,async,no_root_squash) 127.0.0.1/8
(rw,async,no_root_squash)

Kernelsymbols:
Linux spinvis 2.6.14.2 #1 SMP Wed Feb 8 23:58:06 CET 2006 i686 Intel
(R) Xeon(TM) CPU 2.80GHz GenuineIntel GNU/Linux

Similar behaviour is observed with gentoo-sources-2.6.14-r5, same
options.

gzcat /proc/config.gz | grep NFS

CONFIG_NFS_FS=y
CONFIG_NFS_V3=y
CONFIG_NFS_V3_ACL=y
# CONFIG_NFS_V4 is not set
# CONFIG_NFS_DIRECTIO is not set
CONFIG_NFSD=y
CONFIG_NFSD_V2_ACL=y
CONFIG_NFSD_V3=y
CONFIG_NFSD_V3_ACL=y
# CONFIG_NFSD_V4 is not set
CONFIG_NFSD_TCP=y
# CONFIG_ROOT_NFS is not set
CONFIG_NFS_ACL_SUPPORT=y
CONFIG_NFS_COMMON=y


#root@cl36 ~ 20:29:44 > mount
<partly snipped>
10.10.0.80:/data/tools on /root/tools type nfs
(rw,intr,lock,tcp,nfsvers=3,addr=10.10.0.80)
#root@cl36 ~ 20:29:56 > for i in `seq 1 30`; do dd count=1000 if=/dev/
zero of=/root/tools/test.tst; ls -la /root/tools/test.tst ; rm /root/
tools/test.tst ; done
1000+0 records in
1000+0 records out
dd: closing output file `/root/tools/test.tst': No space left on device
-rw-r--r--  1 root root 163840 Feb  8 20:30 /root/tools/test.tst
1000+0 records in
1000+0 records out
dd: closing output file `/root/tools/test.tst': No space left on device
-rw-r--r--  1 root root 98304 Feb  8 20:30 /root/tools/test.tst
1000+0 records in
1000+0 records out
dd: closing output file `/root/tools/test.tst': No space left on device
-rw-r--r--  1 root root 98304 Feb  8 20:30 /root/tools/test.tst
1000+0 records in
1000+0 records out
dd: closing output file `/root/tools/test.tst': No space left on device
-rw-r--r--  1 root root 131072 Feb  8 20:30 /root/tools/test.tst
1000+0 records in
1000+0 records out
dd: closing output file `/root/tools/test.tst': No space left on device
-rw-r--r--  1 root root 163840 Feb  8 20:30 /root/tools/test.tst
<similar thus sniped>

I've so far found this:
http://lwn.net/Articles/150580/

Which seems to indicate that RAID + LVM + complex storage and
4KSTACKS can cause problems. However I can't find the 4KSTACK symbol
anywhere in my config. Can't find the 8KSTACK symbol anywhere either :-(

For those wondering.... no it's not out of space:

10.10.0.80:/data/tools                      9.0T  204G  8.9T   3% /
root/tools

There's nothing in syslog in either case (loopback mount or remote
machine mount or server)

We're using reiserfsv3. It's a raid-50 machine based on two raid-50
arrays of 4,55 Tb handled  by the hardware controller.

The two raid-50 arrays are "glued" together using LVM2:

--- Volume group ---
   VG Name               data-vg
   System ID
   Format                lvm2
   Metadata Areas        2
   Metadata Sequence No  2
   VG Access             read/write
   VG Status             resizable
   MAX LV                0
   Cur LV                1
   Open LV               1
   Max PV                0
   Cur PV                2
   Act PV                2
   VG Size               9.09 TB
   PE Size               4.00 MB
   Total PE              2384134
   Alloc PE / Size       2359296 / 9.00 TB
   Free  PE / Size       24838 / 97.02 GB
   VG UUID               dyDpX4-mnT5-hFS9-DX7P-jz63-KNli-iqNFTH

--- Physical volume ---
   PV Name               /dev/sda1
   VG Name               data-vg
   PV Size               4.55 TB / not usable 0
   Allocatable           yes (but full)
   PE Size (KByte)       4096
   Total PE              1192067
   Free PE               0
   Allocated PE          1192067
   PV UUID               rfOtx3-EIRR-iUx7-uCSl-h9kE-Sfgu-EJCHLR

   --- Physical volume ---
   PV Name               /dev/sdb1
   VG Name               data-vg
   PV Size               4.55 TB / not usable 0
   Allocatable           yes
   PE Size (KByte)       4096
   Total PE              1192067
   Free PE               24838
   Allocated PE          1167229
   PV UUID               5U0F3v-ZUag-pRcA-FHvo-OJeD-1q9g-IthGQg

--- Logical volume ---
   LV Name                /dev/data-vg/data-lv
   VG Name                data-vg
   LV UUID                0UUEX8-snHA-dYc8-0qLL-OSXP-kjoa-UyXtdI
   LV Write Access        read/write
   LV Status              available
   # open                 2
   LV Size                9.00 TB
   Current LE             2359296
   Segments               2
   Allocation             inherit
   Read ahead sectors     0
   Block device           253:3

Based on responses from a different mailinglist and google I tried unfsd
  the userspace nfsd implementation which appears to work fine (still
testing) The above test-case works for both loopback and remote mounted
filesystems.

Update: The Unfsd suffers from the same problem, but has a larger 
filesize as threshold. We're seeing the same behaviour with the 
following testcase:

for i in `seq 1 10`; do dd count=400000 bs=1024 if=/dev/zero 
of=/root/test-tools/test.tst; ls -lha /root/test-tools/test.tst ; rm 
/root/test-tools/test.tst ; done

400000+0 records in
400000+0 records out
dd: closing output file `/root/test-tools/test.tst': No space left on device
-rw-r--r--  1 root root 328K Feb 22 09:53 /root/test-tools/test.tst
400000+0 records in
400000+0 records out
dd: closing output file `/root/test-tools/test.tst': No space left on device
-rw-r--r--  1 root root 176K Feb 22 09:53 /root/test-tools/test.tst

If there's any more info you need, please let me know.

Regards,

Ramon
--
If to err is human, I'm most certainly human.




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