RE: PERC3/DC, PERC4/DC Write Performance

This should be somewhat expected IMO. A cluster configuration (by concept, not implemenation) requires
that nodes in the cluster not cache I/O as a shared storage device is used for maintaining data integrity
between members. Could Dell/RedHat throw up disclaimers that say implementing a cluster configuration
will reduce the overall bandwidth you can achieve with your RAID card? Sure..., but for the most part I
think it's something that should be understood by anyone charged with building high availability
clusters. 

  ---Anthony

	-----Original Message----- 
	From: linux-poweredge-admin <at> dell.com on behalf of Richard, WhidbeyNet NOC 
	Sent: Fri 1/2/2004 12:20 PM 
	To: linux-poweredge <at> dell.com 
	Cc: 
	Subject: PERC3/DC, PERC4/DC Write Performance
	
	

	We purchased four dual-2.8Ghz 2650s, with PERC3/DC cards, along with
	two PowerVault 220S arrays (Ultra320 version), to create two storage
	clusters as recommended by Dell Power Solutions and Red Hat Enterprise.
	
	Cluster testing went relatively smoothly. Failover worked under both
	RHEL AS 2.1 and 3.0. However, we noticed writes to the shared storage
	were slower than expected. So, we went back to a basic configuration
	with factory defaults to diagnose the problem:
	
	With a single 36gb-10K-U320 disk in the PV220S, connected to one 2650,
	on RedHat 9 installed by the Open Manage CD (v7.5), no clustered SCSI,
	a sequential write could be done at 20 MB/s.