Hi Bruce,
thanks for answering, I understand your response, but the problem is not
exactly the disk writing or disk synchronization.
I tried to do a simple test just in one host so the network has been
keep out. (Just the network interface could be taken into account.)
I have a bare metal host:
With this simple features:
O.S:
CentOS Linux release 7.4.1708 (Core)
Kernel:
Linux cld-ctrl-pa-02.cloud.pd.infn.it 3.10.0-693.2.2.el7.x86_64 #1 SMP
Tue Sep 12 22:26:13 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
disk:
Disk /dev/sda: 500.1 GB, 500107862016 bytes, 976773168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x000709ef
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 2099199 1048576 83 Linux
/dev/sda2 2099200 18876415 8388608 82 Linux swap / Solaris
/dev/sda3 18876416 976773119 478948352 83 Linux
controller disk:
IDE interface: Intel Corporation 82801JI (ICH10 Family) 4 port SATA IDE
Controller #1
I have this rpms for nfs and rpc:
[ ~]# rpm -qa | grep nfs
libnfsidmap-0.25-17.el7.x86_64
nfs-utils-1.3.0-0.48.el7_4.1.x86_64
[ ~]# rpm -qa | grep rpc
libtirpc-0.2.4-0.10.el7.x86_64
rpcbind-0.2.0-42.el7.x86_64
I try in direcory /nfstest to untar my file I obtain:
[ ~]# time tar zxvf root_v6.08.06.Linux-centos7-x86_64-gcc4.8.tar.gz
....
real 0m7.324s
user 0m7.018s
sys 0m2.474s
In this case you should say there be a cache in memory of kernel and
command tar, so I try to use the option -w for tar the help say:
-w, --interactive, --confirmation
ask for confirmation for every action
So I think I force the tar command to do each file a file open and a
file close I use this command:
[ ~]# time yes y | tar xzvfw
root_v6.08.06.Linux-centos7-x86_64-gcc4.8.tar.gz
....
sreal 0m7.590s
user 0m7.247s
sys 0m2.569s
I conclude the time to write thoose files in disk is about 8 seconds.
Now in same host (192.168.60.171) I mount /nfstest in same host in
/nfsmount:
[ ~]# cat /etc/exports
/nfstest 192.168.60.0/24(rw,sync,no_wdelay,no_root_squash,no_subtree_check)
mount -t nfs 192.168.60.171:/nfstest/ /nfsmount/
I can see with mount command:
[ ~]# mount
...
192.168.60.171:/nfstest on /nfsmount type nfs4
(rw,relatime,vers=4.1,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,port=0,timeo=600,retrans=2,sec=sys,clientaddr=192.168.60.171,local_lock=none,addr=192.168.60.171)
and I try to untar my file:
[ ~]# time tar zxvf root_v6.08.06.Linux-centos7-x86_64-gcc4.8.tar.gz
....
real 11m27.853s
user 0m8.466s
sys 0m5.435s
So I can not understand why the untar take about 8 seconds and the untar
using directory mounted with nfs in same host take about 11 minutes and
30 seconds, in all the 2 case there be a fo and fc.
I know there are a file open and file close and ACK in the case of NFS
so I expect an overhead, but not a so big overhead. I think there be
something other wrong in the protocol or some timeout somewhere.
I agree with you if I use big file the problem is reduced:
In host:
time tar zxvf test.tgz
Fedora-Server-netinst-x86_64-27-1.6.iso
Fedora-Workstation-Live-x86_64-27-1.6.iso
real 0m52.047s
user 0m24.382s
sys 0m11.597s
Mounted via NFS:
time tar zxvf test.tgz
Fedora-Server-netinst-x86_64-27-1.6.iso
Fedora-Workstation-Live-x86_64-27-1.6.iso
real 0m55.453s
user 0m25.905s
sys 0m10.095s
There is a way to got nfs server from source and build may be with some
verbose logging or build with some optimization to this "performance
problem".
Cheers
Sergio
On 03/05/2018 10:50 PM, J. Bruce Fields wrote:
This should be on a FAQ or something. Anyway, because I've been
thinking about it lately:
On an NFS filesystem, creation of a new file is a synchronous operation:
the client doesn't return from open()/creat() until it's gotten a
response from the server, and the server isn't allowed to respond until
it knows that the file creation has actually reached disk--so it'll
generally be waiting for at least a disk seek or two.
Also when it finishes writing a file and closes it, the close() has to
wait again for the new data to hit disk.
That's probably what dominates the runtime in your case. Take the
number of files in that tarball and divide into the total runtime, and
the answer will probably be about the time it takes to create one file
and commit the write data on close.
As you know, exporting with async is not recommended--it tells the
server to violate the protocol and lie to the client, telling it that
the client that stuff has reached disk when it hasn't really. This
works fine until you have a power outage and a bunch of files that the
file has every right to believe were actually sync'd to disk suddenly
vanish....
Other possible solutions/workarounds:
- use storage that can commit data to stable storage very
quickly: this is what most "real" NFS servers do, generally I
think by including some kind of battery-backed RAM to use as
write cache. I don't know if this is something your HP
controllers should be able to do.
The cheapo version of this approach that I use for my home
server is an SSD with capacitors sufficient to destage the
write cache on shutdown. SSDs marketed as "enterprise" often
do this--look for something like "power loss protection" in
the specs. Since I was too cheap to put all my data on SSDs,
I use an ext4 filesystem on a couple big conventional drives,
mounted with "data=journal" and an external journal on an SSD.
- write a parallel version of tar. Tar would go a lot faster if
it wasn't forced to wait for one file creation before starting
the next one.
- implement NFS write delegations: we've got this on the client,
I'm working on the server. It can't help with the latency of
the original file create, but it should free the client from
waiting for the close. But I don't know if/how much it will
help in practice yet.
- specify/implement NFS directory write delegations: there's not
really any reason the client *couldn't* create files locally
and later commit them to the server, somebody just needs to
write the RFC's and the code.
I seem to remember Trond also had a simpler proposal just to
allow the server to return from a file-creating OPEN without
waiting for disk if it returned a write delegation, but I
can't find that proposal right now....
--b.
On Mon, Mar 05, 2018 at 10:53:21AM +0100, Sergio Traldi wrote:
I have host A and host B using nfs4 or nfs3.
In host A I mount a partition or a disk formatted in ext4 or xfs in
/nfsdisk
I put this file inside the directory:
wget --no-check-certificate https://root.cern.ch/download/root_v6.08.06.Linux-centos7-x86_64-gcc4.8.tar.gz
-O /nfsdisk/root_v6.08.06.Linux-centos7-x86_64-gcc4.8.tar.gz
In host A I export that partition with this line in /etc/exports
/nfsdisk
192.168.1.1.0/24(rw,sync,no_wdelay,no_root_squash,no_subtree_check)
OR using async mode:
/nfsdisk 192.168.1.1.0/24(rw,async,no_root_squash)
From host B I mount via nfs the disk:
mount -t nfs <ip-hostA>:/nfsdisk /nfsdisk
and I obtain something similar to (with mount command):
192.168.1.1:/nfstest on /nfstest type nfs4 (rw,relatime,vers=4.1,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,port=0,timeo=600,retrans=2,sec=sys,clientaddr=192.168.1.2,local_lock=none,addr=192.168.1.1)
In host B I exec:
time tar zxvf root_v6.08.06.Linux-centos7-x86_64-gcc4.8.tar.gz
I try with different hosts bare metal or virtual machine and with
different controller.
1) with bare metal host:
1.1) A and B bare metal with CentOS7 with kernel 3.10.0-514.2.2.el7
with nfs-utils-1.3.0-0.48.el7_4.1.x86_64 and
rpcbind-0.2.0-42.el7.x86_64
In host A:
real 0m45.338s
user 0m8.334s
sys 0m5.387s
In Host B I obtain
sync mode:
real 11m56.146s
user 0m9.947s
sys 0m8.346s
async mode:
real 0m46.328s
user 0m8.709s
sys 0m5.747s
1.2) A and B bare metal with Ubuntu 14.04 jessie with kernel
3.13.0-141-generic with nfs-common 1:1.2.8-6ubuntu1.2 - nfs-server
1:1.2.8-6ubuntu1.2 - rpcbind 0.2.1-2ubuntu2.2
In host A:
real 0m10.667s
user 0m7.856s
sys 0m3.190s
In host B:
sync mode:
real 9m45.146s
user 0m9.697s
sys 0m8.037s
async mode:
real 0m14.843s
user 0m7.916s
sys 0m3.780s
1.3) A and B bare metal with Scientific Linux 6.2 with Kernel
2.6.32-220.el6.x86_64 with nfs-utils-1.2.3-15.el6.x86_64 -
rpcbind-0.2.0-13.el6_9.1.x86_64
In host A:
real 0m5.943s
user 0m5.611s
sys 0m1.585s
In host B:
sync mode:
real 8m37.495s
user 0m5.680s
sys 0m3.091s
async mode:
real 0m21.121s
user 0m5.782s
sys 0m3.089s
2) with Virtual Machine Libvirt KVM
2.1) A and B virtual with CentOS7 with kernel 3.10.0-514.2.2.el7
with nfs-utils-1.3.0-0.48.el7_4.1.x86_64 and
rpcbind-0.2.0-42.el7.x86_64
In host A:
real 0m46.126s
user 0m9.034s
sys 0m6.187s
In Host B I obtain
sync mode:
real 12m31.167s
user 0m9.997s
sys 0m8.466s
async mode:
real 0m45.388s
user 0m8.416s
sys 0m5.587s
2.2) A and B virtual with Ubuntu 14.04 jessie with kernel
3.13.0-141-generic with nfs-common 1:1.2.8-6ubuntu1.2 - nfs-server
1:1.2.8-6ubuntu1.2 - rpcbind 0.2.1-2ubuntu2.2
In host A:
real 0m10.787s
user 0m7.912s
sys 0m3.335s
In Host B I obtain
sync mode:
real 11m54.265s
user 0m8.264s
sys 0m6.541s
async mode:
real 0m11.457s
user 0m7.619s
sys 0m3.531s
Just in two other bare metal hosts I have same situation of 1.3 (old
O.S. and old nfs) and I obtain sync and asyc mode in host B similar
in about:
real 0m37.050s
user 0m9.326s
sys 0m4.220s
in that case the host A has a controller RAID bus controller:
Hewlett-Packard Company Smart Array G6 controllers (rev 01)
Now my question why is there to much difference from sync and async mode?
I try to optimize network in A and B, I try to mount with different
rsize and wsize in B host, I try to change timeo in nfs from B.|
I try to to increase nfsd threads in host A.
I try to change disk scheduler ( /sys/block/sda/queue/scheduler noop
deadline [cfq]) in host A.
I try to use NFS3.
I observe some little improvement in some case but the gap from
async and sync is always very high, except for the bare metal with
G6 array controller.
We would like to use nfs with sync for our infrastructure, but we
can not loose to much performance.
Is there a way to use sync mode with some specific parameter and
improve considerably performance?
Thanks in advance for any hint.
Cheers
Sergio
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
