Re: [Xen-users] IOwaits over NFS

We`ve used various NFS parameters in our testing to resolve this. Here are three different examples of what we have used on a single machine, with no significant improvement:

1) defaults,auto,tcp,bg,hard,intr,noatime 0 0

2) auto,noatime,rsize=32768,wsize=32768,bg,nfsvers=3,intr,tcp,retrans=0 0 0

3) noatime,bg,intr,nolock,tcp 0 0

Thanks.

From: Ribeiro Emerson Gomes

Sent: Tuesday, September 14, 2010 4:20 PM

To: Geoff Galitz ; xen-users@xxxxxxxxxxxxxxxxxxx

Subject: RE: [Xen-users] IOwaits over NFS

Please inform the parameters you use in fstab when you mount your NFS share.

Something like this:

<server>:/<share> <mountpoint> nfs rsize=8192, wsize=8192, timeo=14, intr, tcp, bg, rw, bg, hard, nointr, rsize=32768, wsize=32768, tcp, actimeo=0, vers=3,timeo=600

Emerson

-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Geoff Galitz
Sent: Tuesday, September 14, 2010 11:04 AM
To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] IOwaits over NFS

Hello.

We have a number of Xen 3.4.2. boxes which have constant iowaits at around
10% with spikes up to 100% when accessing data over NFS. We have been
unable to nail down the issue. Any advice?

System info:

release                : 2.6.18-194.3.1.el5xen
version                : #1 SMP Thu May 13 13:49:53 EDT 2010
machine                : x86_64
nr_cpus                : 16
nr_nodes               : 1
cores_per_socket       : 4
threads_per_core       : 2
cpu_mhz                : 2261
hw_caps                :
bfebfbff:28100800:00000000:00000340:009ce3bd:00000000:00000001:00000000
virt_caps              : hvm
total_memory           : 32758
free_memory            : 3974
node_to_cpu            : node0:0-15
node_to_memory         : node0:3974
xen_major              : 3
xen_minor              : 4
xen_extra              : .2
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32
hvm-3.0-x86_32p hvm-3.0-x86_64
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : unavailable
cc_compiler            : gcc version 4.1.2 20080704 (Red Hat 4.1.2-44)
cc_compile_by          : root
cc_compile_domain      : gitco.tld
cc_compile_date        : Wed Nov 11 21:16:28 CET 2009
xend_config_format     : 4

And lsmod from a VM:

Module                  Size Used by
nfsd                  284041 17
exportfs               38849 1 nfsd
auth_rpcgss            81889 1 nfsd
ipv6                  424737 24
xfrm_nalgo             43333 1 ipv6
crypto_api             42945 1 xfrm_nalgo
i2c_dev                43849 0
i2c_core               56129 1 i2c_dev
nfs                   289549 1
lockd                  99185 3 nfsd,nfs
fscache                52385 1 nfs
nfs_acl                36673 2 nfsd,nfs
sunrpc                197513 18 nfsd,auth_rpcgss,nfs,lockd,nfs_acl
iptable_filter         36161 1
ip_tables              55329 1 iptable_filter
x_tables               50377 1 ip_tables
dm_mirror              54345 0
dm_multipath           55385 0
scsi_dh                41665 1 dm_multipath
scsi_mod              197337 1 scsi_dh
parport_pc             62313 0
lp                     47121 0
parport                73293 2 parport_pc,lp
pcspkr                 36289 0
xennet                 61129 0 [permanent]
dm_raid45              98897 0
dm_message             36161 1 dm_raid45
dm_region_hash         46401 1 dm_raid45
dm_log                 44993 3 dm_mirror,dm_raid45,dm_region_hash
dm_mod                100753 4 dm_mirror,dm_multipath,dm_raid45,dm_log
dm_mem_cache           39617 1 dm_raid45
ext3                  168529 1
jbd                    94257 1 ext3
uhci_hcd               57561 0
ohci_hcd               56053 0
ehci_hcd               65869 0
xenblk                 50729 1

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Re: [Xen-users] IOwaits over NFS