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List: aix-l
Subject: Re: Striping on striping - good, bad, indifferent?
From: "Davignon, Edward" <Edward.Davignon () ENERGYEAST ! COM>
Date: 2007-05-29 16:23:26
Message-ID: 873F7EFCE3CA454AA6D3AC34FAEA51300179D508 () ROCMSGCL02 ! Energyeast ! net
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Since AIX LVM does striping at the LV level, wouldn't the striping
information be in the VGDAs on the storage hardware (with a copy in the
ODM on the host)?
The performance hit with striping usually comes when your stripe size is
significantly larger than your average read size (or write size). The
filemon command can be used to monitor both average read and average
write size on AIX. Based on the average size of the disk I/Os for your
particular application and the physical properties of your disks
(optimal size of a reads and writes), you could determine the optimal
size of the RAID stripes and the number of disks to stripe across.
"Vertical" striping could be used to extend the number of disks passed
the maximum number of physical disks allowed on your "horizontal"
subsystem (i.e. SSA RAID controller).
Edward.Davignon@energyeast.com
Lead Analyst - Distributed Systems
Utility Shared Services - IT
Energy East Corporation
________________________________
From: IBM AIX Discussion List [mailto:aix-l@Princeton.EDU] On Behalf Of
Rob Forkner
Sent: Tuesday, May 29, 2007 10:15 AM
To: aix-l@Princeton.EDU
Subject: Re: Striping on striping - good, bad, indifferent?
You can do this, the hardware would take care of two of the raid layers,
and the OS would take care of the last one, so I wouldn't expect a big
performance hit (per se). Here's the caveat (and it may not be a big
one to you)... all the vertical raid information resides on the host and
not the hardware. If something happens to that host, you will not be
able to access that information.
On 5/23/07, Vincent D'Antonio <dantoniov@gmail.com> wrote:
Roger,
If you are doing hardware striping with mirrors I would not do it on the
OS side using two different striping had caused preformance problems. I
don't know if that is the case today. What I would do is when creating
the LV set RANGE of physical volumes to MAX this is evenly put your
PP's across both volumes, almost like a strip without the headaches.
This gives you the greatest use of you hardware strip/mirror.
HTH
Vince
On 5/22/07, Roger Deschner <rogerd@uic.edu> wrote:
I'm setting up a Logical Volume which will consist of two identical
hdisks. Each hdisk will actually be a hardware RAID10 array. (SSA in
this case, though the underlying hardware technology shouldn't matter.)
Within AIX JFS2, should I stripe between those two hdisks, or not? The
application will be /var/spool/mail, so very few of the reads or writes
will exceed the PP size of the VG. Are there any peculiar issues here to
be aware of, such as the relationship of the hardware (SSA) stripe size
to the AIX JFS2 stripe size?
What I am hoping for is to get the benefits of striping across all the
physical disks in both of the arrays, thereby overcoming the 8-way
stripe limit in SSA.
Roger Deschner University of Illinois at Chicago rogerd@uic.edu
==== "Research is what I'm doing when I don't know what I'm doing." ====
========================= -- Wernher von Braun =========================
--
Robert Forkner
Manager of Systems and Operations
Abilene Christian University
325.674.2647
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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Since AIX LVM does striping at the <st1:City
w:st="on"><st1:place w:st="on">LV</st1:place></st1:City> level, wouldn’t
the striping information be in the VGDAs on the storage hardware (with a copy
in the ODM on the host)?<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<div>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>The performance hit with striping usually
comes when your stripe size is significantly larger than your average read size
(or write size). The filemon command can be used to monitor both average
read and average write size on AIX. Based on the average size of the disk
I/Os for your particular application and the physical properties of your disks
(optimal size of a reads and writes), you could determine the optimal size of
the RAID stripes and the number of disks to stripe across. \
“Vertical” striping could be used to extend the number of disks passed \
the maximum number of physical disks allowed on your “horizontal” \
subsystem (i.e. SSA RAID controller).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><strong><b><font size=2 color=gray face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:gray'><a
href="mailto:Edward.Davignon@energyeast.com">Edward.Davignon@energyeast.com</a></span></font></b></strong><b><font
size=2 color=gray face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:gray;font-weight:bold'><br>
<strong><b><font face=Arial><span style='font-family:Arial'>Lead Analyst -
Distributed Systems</span></font></b></strong><br>
<strong><b><font face=Arial><span style='font-family:Arial'>Utility Shared
Services - IT</span></font></b></strong><br>
<strong><b><font face=Arial><span style='font-family:Arial'>Energy East
Corporation</span></font></b></strong><br>
</span></font></b><o:p></o:p></p>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=3 width="100%" align=center tabindex=-1>
</span></font></div>
<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'> IBM AIX
Discussion List [mailto:aix-l@Princeton.EDU] <b><span style='font-weight:bold'>On
Behalf Of </span></b>Rob Forkner<br>
<b><span style='font-weight:bold'>Sent:</span></b> Tuesday, May 29, 2007 10:15
AM<br>
<b><span style='font-weight:bold'>To:</span></b> aix-l@Princeton.EDU<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: Striping on striping
- good, bad, indifferent?</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>You can do this, the
hardware would take care of two of the raid layers, and the OS would take care
of the last one, so I wouldn't expect a big performance hit (per se).
Here's the caveat (and it may not be a big one to you)... all the vertical raid
information resides on the host and not the hardware. If something
happens to that host, you will not be able to access that information. \
<o:p></o:p></span></font></p>
<div>
<p class=MsoNormal><span class=gmailquote><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>On 5/23/07, <b><span style='font-weight:bold'>Vincent
D'Antonio</span></b> <<a \
href="mailto:dantoniov@gmail.com">dantoniov@gmail.com</a>> \
wrote:</span></font></span><o:p></o:p></p>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Roger,<o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>If you are doing hardware striping with mirrors I would not do it
on the OS side using two different striping had caused preformance
problems. I don't know if that is the case today. What I would do is when
creating the <st1:City w:st="on"><st1:place w:st="on">LV</st1:place></st1:City>
set RANGE of physical volumes to MAX this is evenly put your PP's
across both volumes, almost like a strip without the headaches. This
gives you the greatest use of you hardware strip/mirror. \
<o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>HTH<o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Vince<br>
<o:p></o:p></span></font></p>
</div>
<div><span id="q_112b8bfe3bdd813f_1">
<div>
<p class=MsoNormal><span class=gmailquote><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>On 5/22/07, <b><span style='font-weight:bold'>Roger
Deschner</span></b> <<a href="mailto:rogerd@uic.edu" \
target="_blank">rogerd@uic.edu</a>>
wrote: </span></font></span><o:p></o:p></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>I'm setting up a Logical Volume which will consist of two identical<br>
hdisks. Each hdisk will actually be a hardware RAID10 array. (SSA in <br>
this case, though the underlying hardware technology shouldn't matter.)<br>
<br>
Within AIX JFS2, should I stripe between those two hdisks, or not? The<br>
application will be /var/spool/mail, so very few of the reads or writes <br>
will exceed the PP size of the VG. Are there any peculiar issues here to<br>
be aware of, such as the relationship of the hardware (SSA) stripe size<br>
to the AIX JFS2 stripe size?<br>
<br>
What I am hoping for is to get the benefits of striping across all the <br>
physical disks in both of the arrays, thereby overcoming the 8-way<br>
stripe limit in SSA.<br>
<br>
Roger Deschner University of Illinois at <st1:City
w:st="on"><st1:place w:st="on">Chicago</st1:place></st1:City>
<a href="mailto:rogerd@uic.edu" target="_blank">rogerd@uic.edu</a><br>
==== "Research is what I'm doing when I don't know what I'm doing."
==== <br>
========================= -- Wernher von Braun \
=========================<o:p></o:p></span></font></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
<br>
<o:p></o:p></span></font></p>
</div>
</div>
</span>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
<br clear=all>
<br>
-- <br>
Robert Forkner<br>
Manager of Systems and Operations<br>
<st1:place w:st="on"><st1:PlaceName w:st="on">Abilene</st1:PlaceName> <st1:PlaceName
w:st="on">Christian</st1:PlaceName> <st1:PlaceName \
w:st="on">University</st1:PlaceName></st1:place><br> 325.674.2647 \
<o:p></o:p></span></font></p>
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