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The network interconnect between the vms is slow. What<br>
would have helped is the sys and user times. But my guess<br>
is that that is low. Most of it is spent in wall time.<br>
<br>
In mainline, o2net dumps stats showing the ping time between<br>
nodes. Unfortunately this kernel is too old.<br>
<br>
On 08/18/2011 04:24 PM, Nick Geron wrote:
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<p class="MsoNormal">Greetings,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I’m rather new to OCFS2, so please forgive
any glaringly ignorant statements.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I’m evaluating file systems and storage
layout for a simple 2 node mail cluster using Maildir email
directories. I have created a 2 node cluster with related
tutorials. The problem I’m seeing is that general file access
using cp, find, du, ls, etc. is a significant factor slower on
ocfs2 than alternative local and remote disk configurations.
I’m hoping someone can clue me into whether this behavior is
normal, or if I’m missing something in my lab.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">*Hosts are identical CentOS 5.5 virtual
machines (VMware) with 2.6.18-238.19.1.el5. (2 ESXi hosts)<o:p></o:p></p>
<p class="MsoNormal">*OCFS2 build is
ocfs2-2.6.18-238.19.1.el5-1.4.7-1.el5 (tools v 1.4.4-1.el5).<o:p></o:p></p>
<p class="MsoNormal">*SAN is an EMC Clariion. LUN is accessed
via iSCSI with EMC PowerPath 5.5.0.00.00-275<o:p></o:p></p>
<p class="MsoNormal">*Nodes share a gigabit network for their
private interconnect via two interconnected switches (ESXi
host into each).<o:p></o:p></p>
<p class="MsoNormal">*Test data is a 181MB Maildir directory
(~12K emails) copied to various types of storage.<o:p></o:p></p>
<p class="MsoNormal">*Tests involve simple bash scripts running
(bash) time with the mentioned command line utilities and
strace inspection.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The OCFS2 file system was created with the
following (mount cannot load xattr or extended-slotmap added
with max-features):<o:p></o:p></p>
<p class="MsoNormal">mkfs.ocfs2 -N 2 -T mail
--fs-features=backup-super,sparse,unwritten,inline-data -v
/dev/emcpowera<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Mount options are limited to ‘_netdev’ at
the moment. I’ve read a bit about changing ‘data’ from
ordered to writeback, but that seems to be related to waits on
flushing cache to disk. So far, I’m just focusing on
reads/lstats.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">With a maildir in place, any operation that
must inspect all files takes quite a while to complete without
cached entries. The alarming thing is the discrepancy between
my OCFS2 data and identical data on local, NFS and iSCSI
mounts.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Here’s some simple data that should
illustrate my problem and my confusion:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Command: ‘du –hs
/path/to/maildir/on/various/mounts<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Storage Real time to
complete Min:Sec<o:p></o:p></p>
<p class="MsoNormal">----------------------------------------------------------------------<o:p></o:p></p>
<p class="MsoNormal">Local disk 0:0.078<o:p></o:p></p>
<p class="MsoNormal">NFS 0:2<o:p></o:p></p>
<p class="MsoNormal">iSCSI (EXT3) 0:1.7<o:p></o:p></p>
<p class="MsoNormal">iSCSI (OCFS2) 4:24<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Other tests including recursive chowns or
chmods, and ls report similar results.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Most telling is perhaps strace output.
There I can see system calls on individual Maildir files.
Times between each call/operation take far longer on OCFS2 and
there is no hint of externally derived waits. Nor are there
any indicators of load issues from competing processes;
nothing else (significant) is going on and du has full reign
of the OS resources.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Output from strace with –tt –T using du –hs
against the Maildir on my EXT3 iSCSI LUN (/dev/emcpowerb1)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">18:03:17.572879
lstat("1313705228.000737.mbox:2,S", {st_mode=S_IFREG|0644,
st_size=715, ...}) = 0 <0.000018><o:p></o:p></p>
<p class="MsoNormal">18:03:17.572944
lstat("1313705228.008426.mbox:2,S", {st_mode=S_IFREG|0644,
st_size=2779, ...}) = 0 <0.000024><o:p></o:p></p>
<p class="MsoNormal">18:03:17.573016
lstat("1313705228.006345.mbox:2,S", {st_mode=S_IFREG|0644,
st_size=2703, ...}) = 0 <0.000020><o:p></o:p></p>
<p class="MsoNormal">18:03:17.573083
lstat("1313705228.001305.mbox:2,S", {st_mode=S_IFREG|0644,
st_size=1831, ...}) = 0 <0.000017><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Output from the same trace against the
OCFS2 store<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">18:06:52.876713
lstat("1313707554.003441.mbox:2,S", {st_mode=S_IFREG|0644,
st_size=2322, ...}) = 0 <0.040896><o:p></o:p></p>
<p class="MsoNormal">18:06:52.917723
lstat("1313707554.003442.mbox:2,S", {st_mode=S_IFREG|0644,
st_size=2316, ...}) = 0 <0.040663><o:p></o:p></p>
<p class="MsoNormal">18:06:52.958473
lstat("1313707554.003443.mbox:2,S", {st_mode=S_IFREG|0644,
st_size=2899, ...}) = 0 <0.000938><o:p></o:p></p>
<p class="MsoNormal">18:06:52.959471
lstat("1313707554.003444.mbox:2,S", {st_mode=S_IFREG|0644,
st_size=2522, ...}) = 0 <0.001106><o:p></o:p></p>
<p class="MsoNormal">18:06:52.960641
lstat("1313707554.003445.mbox:2,S", {st_mode=S_IFREG|0644,
st_size=3451, ...}) = 0 <0.039904><o:p></o:p></p>
<p class="MsoNormal">18:06:53.000644
lstat("1313707554.003446.mbox:2,S", {st_mode=S_IFREG|0644,
st_size=3150, ...}) = 0 <0.041060><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Is this normal behavior for a current
kernel and the most recent 1.4.7 code? Does someone suspect
I’ve blundered somewhere along the way? I’ve seen many posts
to this list related to a mail cluster setup like mine. Is
anyone on the list running a production mail cluster with
OCFS2? I apologize for the length of this email. Thanks.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">-Nick Geron<o:p></o:p></p>
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