JWColby
jwcolby at colbyconsulting.com
Thu Nov 16 10:24:25 CST 2006
Rocky, Flash have faster access times than hard drives, but slower read/write times. IOW, the drive has to rotate to get the data under the head, which can be milliseconds, but once the data starts to stream on/off the disk, it does so faster than flash. The other issue with Flash is that they can only WRITE any given memory location a certain number of times before the location "wears out". Associated with this is the problem that flash is written in pages, not individual bytes. Which means that if only a single byte of a page changes, the entire page has to be written anyway. The question is, is this an issue? It really depends on how the drive is used. Many files are written once and then stay there for a LONG time. Word documents, excel spreadsheets etc. OTOH, things like the area of a disk used to contain data for a SQL Server or Access database might change many times per second, just depending on usage of the database. OTOH, flash is purely electronic vs. mechanical for hard disks. Electronic circuit failures group into two types, electrostatic and mechanical (yes mechanical). We all know the issue with ESD. The mechanical failures with chips come into play with the bonding wires that link the chips to the external pins leading off the container. These wires are made of gold, and are finer than a human hair. They will fail from flexing caused by heating up and down as the chip is turned on / off. You might have noticed that incandescent light bulbs never seem to just fail once they are on, but rather they fail (typically) when you turn the light bulb on. Incandescent lights are a hot wire. The wire flexes as it heats up and the metal wire expands. Eventually that flexing causes a stress fracture. The same phenomenon occurs in electronic chips, though much slower simply because the heat is usually less so the amount of flexing is less. Unfortunately neither of these failure types is the issue with FLASH "max write cycles". Anyway... If electronic chips were never turned off, and never subjected to ESD, they would likely last for centuries, or perhaps "forever". The reality is that rotating and solid state memories both have their uses and the boundaries of where each is most useful shift back and forth but both will be around for awhile. There are other "flash" (solid state) memories on the horizon though, based on magnetics and the likes. We'll have to wait and see how they effect the equation. You have heard that Vista can use FLASH for an intermediate level cache. John W. Colby Colby Consulting www.ColbyConsulting.com -----Original Message----- From: dba-tech-bounces at databaseadvisors.com [mailto:dba-tech-bounces at databaseadvisors.com] On Behalf Of Beach Access Software Sent: Thursday, November 16, 2006 10:48 AM To: 'Discussion of Hardware and Software issues' Subject: Re: [dba-Tech] Software on a USB Drive True. Can a 100GB flash drive be far off? And at a price competitive with a hard drive? Do you know anything about their reliability? Ever hear of a flash drive failing? And are the speeds of reading and writing comparable? The 8GB one I used seemed to generate a lot of heat. I wonder if they will degrade quickly from their own heat. Rocky -----Original Message----- From: dba-tech-bounces at databaseadvisors.com [mailto:dba-tech-bounces at databaseadvisors.com] On Behalf Of John Bartow Sent: Thursday, November 16, 2006 7:37 AM To: 'Discussion of Hardware and Software issues' Subject: Re: [dba-Tech] Software on a USB Drive You really have to want a lot of data in your pocket to spend that kind of cash, eh? :o) Kind of a sign of times to come though. Pretty soon we'll be using solid state storage instead of hard "disks" for our storage needs. -----Original Message----- From: dba-tech-bounces at databaseadvisors.com [mailto:dba-tech-bounces at databaseadvisors.com] On Behalf Of Beach Access Software Sent: Thursday, November 16, 2006 12:26 AM I see it now - $1500. But I'll wait until next month when I can get the $1400 rebate. Rocky _______________________________________________ dba-Tech mailing list dba-Tech at databaseadvisors.com http://databaseadvisors.com/mailman/listinfo/dba-tech Website: http://www.databaseadvisors.com -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.430 / Virus Database: 268.14.6/535 - Release Date: 11/15/2006 3:47 PM _______________________________________________ dba-Tech mailing list dba-Tech at databaseadvisors.com http://databaseadvisors.com/mailman/listinfo/dba-tech Website: http://www.databaseadvisors.com