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Old 06-20-2008, 04:55 PM
Florin Andrei
 
Default 3ware performance in CentOS

Florin Andrei wrote:


Anyway, I did a test with the 2.6.18-93.el5.bz444759 kernel and there's
no difference: 65 minutes, 27 MB/s. Looks like it doesn't matter which
kernel I use, at least for this simple test with dd.


I wonder if a test closer to real life, such as reading/writing stuff
from/to MySQL, would produce different results. I guess there's only one
way to find out. ;-)


As a side note, the artificial benchmark reveals a huge difference
between Ext3 and XFS - the latter is much faster when writing. Might be
an artifact of some setting (after all, I do use a hardware RAID card).
But the difference is very real.


I was planning to use XFS anyway, so I'm not sure if I'll spend too much
time troubleshooting Ext3.


I don't think this is some kind of hidden effect of the MWI bug.

--
Florin Andrei

http://florin.myip.org/
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Old 06-20-2008, 05:05 PM
Joshua Baker-LePain
 
Default 3ware performance in CentOS

On Fri, 20 Jun 2008 at 9:55am, Florin Andrei wrote


Florin Andrei wrote:


Anyway, I did a test with the 2.6.18-93.el5.bz444759 kernel and there's no
difference: 65 minutes, 27 MB/s. Looks like it doesn't matter which kernel
I use, at least for this simple test with dd.


I wonder if a test closer to real life, such as reading/writing stuff
from/to MySQL, would produce different results. I guess there's only one
way to find out. ;-)


As a side note, the artificial benchmark reveals a huge difference between
Ext3 and XFS - the latter is much faster when writing. Might be an artifact
of some setting (after all, I do use a hardware RAID card). But the
difference is very real.


I was planning to use XFS anyway, so I'm not sure if I'll spend too much time
troubleshooting Ext3.


I don't think this is some kind of hidden effect of the MWI bug.


XFS has *always* been faster on 3ware than ext3. RH has never been
interested in looking at why. *shrug*


--
Joshua Baker-LePain
QB3 Shared Cluster Sysadmin
UCSF
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Old 06-20-2008, 05:23 PM
"Jim Perrin"
 
Default 3ware performance in CentOS

On Fri, Jun 20, 2008 at 12:55 PM, Florin Andrei <florin@andrei.myip.org> wrote:

>> Anyway, I did a test with the 2.6.18-93.el5.bz444759 kernel and there's no
>> difference: 65 minutes, 27 MB/s. Looks like it doesn't matter which kernel I
>> use, at least for this simple test with dd.

No. Since you're using the driver from 3ware/amcc you are not going to
experience this particular performance hit. Only if you're using the
stock 3ware driver which is built into the kernel.

> As a side note, the artificial benchmark reveals a huge difference between
> Ext3 and XFS - the latter is much faster when writing. Might be an artifact
> of some setting (after all, I do use a hardware RAID card). But the
> difference is very real.
>
> I was planning to use XFS anyway, so I'm not sure if I'll spend too much
> time troubleshooting Ext3.
>
> I don't think this is some kind of hidden effect of the MWI bug.
>

Nope. This is just a long-standing performance thing. You can tune
ext3 to perform better, but on a 3ware card xfs will win, hands down.


--
During times of universal deceit, telling the truth becomes a revolutionary act.
George Orwell
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Old 06-20-2008, 05:34 PM
John R Pierce
 
Default 3ware performance in CentOS

Jim Perrin wrote:

Nope. This is just a long-standing performance thing. You can tune
ext3 to perform better, but on a 3ware card xfs will win, hands down.



of course, XFS can also fail spectacularly. ext3fs fully journals all
metadata updates. I'm sure this is a major portion of the performance
differences on writes.

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Old 06-20-2008, 05:40 PM
Joshua Baker-LePain
 
Default 3ware performance in CentOS

On Fri, 20 Jun 2008 at 10:34am, John R Pierce wrote


Jim Perrin wrote:

Nope. This is just a long-standing performance thing. You can tune
ext3 to perform better, but on a 3ware card xfs will win, hands down.



of course, XFS can also fail spectacularly. ext3fs fully journals all
metadata updates. I'm sure this is a major portion of the performance
differences on writes.


Every FS can fail spectacularly. XFS (obviosly) journals as well, but it
doesn't force an "ordered" mode as ext3 does by default. However, even if
you mount ext3 with "data=writeback" (which is roughly analogous to XFS'
journaling mode), ext3 still doesn't perform nearly as well as XFS on
3ware.


--
Joshua Baker-LePain
QB3 Shared Cluster Sysadmin
UCSF
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Old 06-20-2008, 05:47 PM
Florin Andrei
 
Default 3ware performance in CentOS

John R Pierce wrote:


of course, XFS can also fail spectacularly. ext3fs fully journals all
metadata updates. I'm sure this is a major portion of the performance
differences on writes.


Actually, I've used XFS since the days it was released as a port to
Linux (and even before that, on Irix, but that's besides the point). I'm
aware it's more fragile than Ext3 - in fact, someone here at the office
made an XFS partition yesterday to do some tests, there was a power
outage last night, and today that partition is corrupted.


I'll use battery backups (duh) and only put on XFS the stuff that needs
good performance, but can be rebuilt from the master data in case
something ugly happens. Like pretty much anything in life, it's a trade-off.


--
Florin Andrei

http://florin.myip.org/
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Old 06-20-2008, 05:57 PM
"Ross S. W. Walker"
 
Default 3ware performance in CentOS

Florin Andrei wrote:

> John R Pierce wrote:
> >
> > of course, XFS can also fail spectacularly. ext3fs fully journals all
> > metadata updates. I'm sure this is a major portion of the performance
> > differences on writes.
>
> Actually, I've used XFS since the days it was released as a port to
> Linux (and even before that, on Irix, but that's besides the point). I'm
> aware it's more fragile than Ext3 - in fact, someone here at the office
> made an XFS partition yesterday to do some tests, there was a power
> outage last night, and today that partition is corrupted.
>
> I'll use battery backups (duh) and only put on XFS the stuff that needs
> good performance, but can be rebuilt from the master data in case
> something ugly happens. Like pretty much anything in life,
> it's a trade-off.

Also to make sure to only use kernel drivers that are solid under
both normal and heavy loads, burn in the hardware sufficiently to
make sure there are no lurking failures and make sure your
applications behave properly.

It's not just power that can stop a server suddenly, but to XFS
the result is the same!

-Ross

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Old 06-30-2008, 06:10 PM
Florin Andrei
 
Default 3ware performance in CentOS

Jim Perrin wrote:


Nope. This is just a long-standing performance thing. You can tune
ext3 to perform better, but on a 3ware card xfs will win, hands down.


Well, after performing more mental ruminations on this subject,
restoring the database in case of a crash might be a pain, so I may have
to avoid XFS in this particular case.


Can somebody recommend a RAID card, about the same price range like the
3ware 9650SE, and with similar features, 8 SATA ports or more, that
works well with CentOS 5 and does not have the Ext3 performance bug?


There's a bunch of cards out there, but I'd like to hear from someone
with first-hand experience with one of them.


--
Florin Andrei

http://florin.myip.org/
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