[Pc_Support] Re: RAID5 Performance -- release 9.2.1.1 for 3Ware 9500S series

[Austin Denyer (Ozz)]

On Thu, 29 Dec 2005 12:11:32 -0800 (PST), "Bryan J. Smith"
<b.j.smith at ieee.org> wrote:
>
> What release?  Make sure you are running with 9.2.1.1 for the
> 9500S -- that means firmware (and BIOS), driver _and_ 3DM2. 
> To match each version against 9.2.1.1, see the release notes:

Hmm - not sure off-hand.  I'll check on Tuesday.  It's brand new
though, and the supplier is _supposed_ to have loaded all the latest
firmware.  They are generally pretty good for that, but no-one is
perfect, so I will check.

> There were some major issues with earlier releases that
> caused serious performance snafus with select RAID-5
> configurations.
> 
> > 4x WD4000YR 400GB SATA HDD
> > Hardware RAID5
> 
> Understand RAID-5 will always be _slower_ than RAID-10.

I do understand that.  All those XORs take time...

> > Installing Debian Linux with 2.6.12-amd64 kernel (I will
> > upgrade to 2.4.14-4-smp-amd64 once base install is
> complete).
> 
> I've personally found the stock kernels to be _horrendous_ in
> updating the 3w-9xxx driver.  To make matters worse, the
> 9500S (9.2.x) and new 9550SX (9.3.x) are not yet unified
> firmware/release-wise.

I'll check into that too.  Thanks.
 
> > Question: how long should such hardware take to format a
> > 1.2Tb /home partition as ext3?  This seems to be taking a
> > very long time (approaching 45 mins, 88% complete).
> > This doesn't sound normal to me.
> 
> It's _not_ unrealistic for "mke2fs -j" to take up to an hour
> per TB to create various structures.  Remember, Ext3
> _preallocates_ inodes.

It just seemed to take a lot longer than I expected compared to the
time it took to format the 100+Gb /home on my workstation.  I was
expecting around 12-15 times longer, but this seemed a lot longer than
that.

> If you are used to ReiserFS, XFS or JFS, which dynamically
> allocate inodes, a large Ext3 format will seem to take
> several orders of magnitude longer.  ;->

I always stick with ext3 these days.  I got burned by ReiserFS a few
years ago - never again.

> P.S.  I really don't like to make Ext3 volumes larger than
> 1TB.  I also like to create at least 2 volumes on any array
> -- for various reasons.  One is reducing any fsck time, if a
> full fsck is required -- especially since I could bring up
> the system with only 1 filesystem mounted (allowing at least
> half the users to work while the other filesystem is fsck'd).
>  Another is not putting all my eggs in one filesystem basket.
>  ;->

If the /home partition was actually gonna be used for user data then
yes, I'd feel the same way, and would have gone for splitting the
partition down.  However, this is not gonna have lots of users, just a
couple of small admin accounts and one huge system account for one
specific application.  

Thanks for the input.  Once again, a wealth of valuable info from TheBS.

Regards,
Ozz.

> *** Speed doesn't kill, difference in speed does ***

PS - Love the .sig #;-D
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