Tweaking Perc 6i for throughput

[Scott R. Ehrlich]

Hello to all:

In light of the email below, I have some PE2950 servers with an MD3000i, 
and ordered the servers with no OS installed.  I've learned that APF comes 
pre-installed, but I performed my own OS install - CentOS 5.2 out-of-box, 
no patches or updates, how do I obtain and install APF to help with 
performance, or will APF do nothing for an iSCSI connection?

Thanks.

Scott

On Thu, 22 Jan 2009, Drew Weaver wrote:

> Sorry (don't like to reply to my own spams) I forgot to mention that in IPERF:
>
> [  3]  0.0-10.0 sec  1.10 GBytes    942 Mbits/sec
>
> So I know the network isn't the bottleneck.
>
> -Drew
>
> -----Original Message-----
> From: linux-poweredge-bounces at dell.com [mailto:linux] On Behalf Of Drew Weaver
> Sent: Thursday, January 22, 2009 9:13 AM
> To: 'linux-poweredge at dell.com'
> Subject: Tweaking Perc 6i for throughput
>
> Sorry for the length.
>
> Hi there,
>
> I am doing some anecdotal 'speed testing' using two 2950s with PERC 6i that are both connected at 1Gbps (4Gbps port channel) to a Cisco 2960G.
>
> On the downloading side I have both a RAID-1 and a RAID-6 volume, on the uploading side I have only a RAID-1 volume.
>
> Some things I've noted:
>
> If APF is enabled on the downloading (wget) side and I download to the RAID-1 volume:
>
> 	The transfer starts out at 50M/s and then pauses and drops down to 20M/s and then goes back up to 50 and then to 30 (the idea is it is all over the map).
>
> 100%[=====================================>] 3,662,573,568 19.5M/s   in 1m 41s
>
> If APF is enabled on the download side and I download to the RAID-6 volume:
>
> 100%[=====================================>] 3,662,573,568 49.0M/s   in 73s
>
> As you can see the RAID-6 volume crushes the RAID-1 Volume.
>
> If I disable APF (raid-1):
>
> The transfer starts out at 110MB/sec (WOW) but quickly drops, it ends up at:
>
> 07:51:08 (44.4 MB/s) - `Fedora-10-i386-DVD.iso.3' saved [3662573568/3662573568]
>
> APF disabled (raid-6)
>
> 07:52:24 (79.2 MB/s) - `Fedora-10-i386-DVD.iso.11' saved [3662573568/3662573568]
>
> So conclusions so far:
>
> --APF kills throughput
> --RAID-1 is slower than RAID-6 (duh)
> --For some reason this card even in RAID-6 generates a lot of IOWAIT and pauses in the transfer.
> --During the transfer the sending server has IOWAIT all over the place (RAID-1)
>
> Does anyone have any tips I can use to improve performance of both APF and the controller(s) both raid-1 and raid-6 themselves?
>
> I am considering changing the sending server to either raid-10 or raid-6, please advise as to what would deliver the best performance.
>
> I'd like to get as close to 'to the wall' as possible.
>
> Thanks,
> -Drew
>
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