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Conference turris::digital_unix

Title:	DIGITAL UNIX(FORMERLY KNOWN AS DEC OSF/1)
Notice:	Welcome to the Digital UNIX Conference
Moderator:	SMURF::DENHAM

Created:	Thu Mar 16 1995
Last Modified:	Fri Jun 06 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	10068
Total number of notes:	35879

9786.0. "Digital Unix installed on HSZ50 raid-5 set" by VAXRIO::LEO () Mon May 12 1997 12:35

    Hi,
    
    	I have an AlphaServer with Digital Unix 4.0B installed on that.
    
    	The system has a KZPSA-BB that is linked to an HSZ50-AJ.
    
    	I have configured 5 RAID-5 sets on the HSZ50 controller.
    
    	Is there any repported problem or performance bottleneck if the 
    Operating System, i.e. Digital Unix,  is installed on a RAID-5 set
    located  at  HSZ50-AJ intead of been installed on an internal RZ29-VW
    disk ?
    
    	Is there any recommendation or rule to be followed regarding the
    placement of the Operating System binaries in this kind of
    configuration ? 
    
    	Any help would be appreciate.
    
    	Thanks in advance.
    
    	Best reagards,
    
    	Leo
        Digital Technical Support

T.R Title User Personal
Name Date Lines

9786.1 SSDEVO::ROLLOW Dr. File System's Home for Wayward Inodes. Sun May 18 1997 14:10 12

T.R	Title	User	Personal Name	Date	Lines
9786.1		SSDEVO::ROLLOW	Dr. File System's Home for Wayward Inodes.	`Sun May 18 1997 14:10`	12
	Even with a good sized write-back cache, write performance to a RAID-5 can be relatively poor compared to the read performance on the same array, or write performance to a mirrored device. Some parts of the system disk will see more write intensive I/O traffic than others and this could affect the system performance. The usual culprits are: primary page/swap /tmp - may appear as write once-read never /var - or the /usr/var of /usr; /var/tmp and log files.

	Even with a good sized write-back cache, write performance
	to a RAID-5 can be relatively poor compared to the read
	performance on the same array, or write performance to a
	mirrored device.  Some parts of the system disk will see
	more write intensive I/O traffic than others and this could
	affect the system performance.  The usual culprits are:

		primary page/swap
		/tmp - may appear as write once-read never
		/var - or the /usr/var of /usr; /var/tmp and
			log files.