[wplug] RAID performance

[Edward Walter]

Patrick,

You might want to look at the forums on storagereview.com.  Some of the 
users there have posted real world numbers and tuning tips for the 3ware 
9500s and comparisons to other 3ware controllers.

Here's where I'd start:

http://forums.storagereview.net/index.php?act=ST&f=2&t=24237

Enjoy.

-Ed

Patrick Wagstrom wrote:
> I'm in the process of speccing out a new machine for a research group 
> here at CMU.  Needs to be fairly beefy, handle about 1TB of MySQL 
> databases, plus room for other computations to take place.  Anyway, 
> we'll put aside all the issues of MySQL and their choice of software, 
> and instead focus on an interesting issue I noticed last night, and 
> I'm looking for some help with it, or someone to double check it.
>
> We've got a machine right now with 4x400GB Hitachi SATA I drives 
> (model HDS724040KLSA80S) connected to a 3ware Escalade 9500S 4 port 
> SATA RAID controller (128MB of ram on the controller).  These drives 
> are structured in RAID 5.  And on the other hand, at home I've got 
> 4x320GB Seagate SATA II (model STS3320620AS) running software raid 5 
> on a MSI K8N-Neo4 Platinum (8x SATA ports).  I went software RAID at 
> home because of cost and because performance isn't overly critical for 
> the home machine because it's just HDTV, which only needs about 2MB/s 
> write speed max.
>
> Anyway, I did some admittedly synthetic benchmarks to compare 
> performance on the system because I wanted to get an idea how much the 
> hardware RAID made a difference, or if we'd be better off getting an 
> additional 2 or 3 500GB drives for the cost of the hardware RAID.  As 
> a final point of comparison, I included my IBM T43p laptop which as a 
> SATA harddrive inside and no RAID.  For read the speeds are averaged 
> over 10 runs of hdparm.  For writes the speed is averaged over 3 
> consecutive runs.  Here's what I found:
>
> using hdparm -tT to get an idea of read speed:
>
> 9500S Hardware: 52MB/s
> K8N Software: 178MB/s
> T43p No Raid: 40MB/s
>
> Then I decided to find some large files and copy them from one 
> location on the drive to another.  This was the best I could do 
> because I didn't want external drives to be the bottleneck and the 
> hardware raid machine has all disks as part of the array:
>
> 9500S Hardware (1.5G file): 24MB/s
> K8N Software (1.1G file): 42MB/s
> T43p No Raid (2.3G file): 11.5MB/s
>
> So, as should be expected the laptop lags behind on just about 
> everything.  However, what I was surprised to find was that software 
> RAID 5 destroyed the hardware RAID 5 in terms of speed.  This leads me 
> to wonder about a few things and I'd like to get other peoples feedback.
>
> Does anyone else have a 3ware 9500s running RAID 5 that they could 
> provide some useful benchmarks from?  Are there tuning parameters I 
> should enact on the 9500s to increase performance?  Should the switch 
> between SATAI and SATAII drives really make that much of difference?  
> My impression is that while SATA II drives theoretically supported 
> 3Gbps they really come nowhere close -- which is what my results show. 
> However, going 3x as fast for reads and 2x as fast for writes on 
> software RAID was quite surprising.
>
> Any comments?
>
> Thanks!
>
> --Patrick
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