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Conference ssag::ask_ssag

Title:	Ask the Storage Architecture Group
Notice:	Check out our web page at http://www-starch.shr.dec.com
Moderator:	SSAG::TERZAN

Created:	Wed Oct 15 1986
Last Modified:	Fri Jun 06 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	6756
Total number of notes:	25276

6756.0. "Help for guideline on EZ54 performance" by HGOV08::ROCKYLAM () Fri Jun 06 1997 06:52

    Dear Team-mate,     
    
    	One of our major customer in Hong Kong they are using DIGITAL
    solid-state disk EZ54R has performance problem, which of course the
    customer pointed out that the EZ54 cannot have 800 I/O's per sce as
    stated in the SOC.
     I have already explained to them for the low transfer control
    circuitry of EZ54 of only 2.5 MB/sec. However, the customer want us to
    give them the guideline on how to achieve 800 I/O /sec as the SOC, what
    is the specification to get this wonderful result. I only need to know
    the specification is good enough, which the customer must need to
    clarify our validity in our SOC.
    On the other hand, we would need to improve their EZ54 performance,
    would someone be kind enough to tell me how to get the document of
    EZ5XX_PERFORMANCE.PS. Since I cannot find it in the following directory
    - BABAGI::LCA:[SPECS.SOLID_STATE.EZXX]
    
    Thank you very much in advance...
    
    Best Regards,
    Rocky Lam
    HK Technical Support

T.R	Title	User	Personal Name	Date	Lines
6756.1	moved..	SUBSYS::VIDIOT::PATENAUDE	Ask your boss for ARRAY's...	`Fri Jun 06 1997 08:43`	13
	Rocky, BABAGI files moved to SUBSYS a long while back. It has been mentioned in here quite a few times and there is a note about it in here.. To answer your question though.. To get max throughput on an EZ5x product you MUST use SMALL I/O's. The unit has a low bandwidth but no seek time so you need to capitalize on THAT by the small I/O's. Roger.
6756.2	notes collision	SUBSYS::BROWN	SCSI and DSSI advice given cheerfully	`Fri Jun 06 1997 08:52`	24
	The documentation moved from BABAGI:: to SUBSYS::. I would like to know more about what sort of performance your customer would like to see. It sounds like the customer asked about megabytes per second, not I/Os per second. As far as I know, the drive is capable of 800 I/Os per second. If each I/O command reads one block, that's a data rate of only 400KB/sec. A disk drive's performance is typically measured two ways: commands per second, and megabytes per second. There is a trade-off between them. If you use larger transfer sizes (16KB per command, 64KB per command, and so on), you can transfer more data per second. If you use smaller transfer sizes, you can issue more commands per second. You can't maximize both at the same time. The hard part is matching the customer's requirements to the devices available. If the customer needs sub-millisecond access time to widely scattered data, use an EZ (solid-state) disk. If he needs the most megabytes per second, get a Winchester disk, and settle for about 300 commands per second on localized data, and maybe 100 commands per second on widely scattered data. It may be difficult to predict which disks and configurations will yield the best performance. What does the customer use the system for?