is it possible to build an all flash memory Hard Drive ?

[Inspirer]

Is the theoretical read/write speed of current flash memory fast enough for usage as the main HD ?
The numbers I read lead me to believe that it is.

If so, what kind of advantages would persuade you to pay x2 for say a HD which is 1/3 the size of a rotating disks HD ?

reliability ?
shock resistance ?
speed (bandwidth + latency) ?
power consumption ?


or, do you think the direction shoud be a very large cache between the HD and RAM ?

 

[Peter]

These have existed for many years already. Drawbacks are price, capacity, speed, and longevity. Flash cells have a limited lifespan on write cycles (100,000 usually), which is quickly reached given the amount of disk activity in standard operating systems.

Embedded systems, particularly for environments that require an extended temperature range or shock/vibration immunity, have been using these drives all the time.

CompactFlash cards btw also have a native IDE mode.

 

[Kuroyama]

Do a search for "solid state hard drive". For instance, a small 512MB solid state drive is $370 below

http://www.memorydepot.biz/diskonmodule/

You can find some which are apparently used by the military at

http://www.bitmicro.com/

 

[damonpip]

Wow, that 32meg one looks like it could be pretty nice, or maybe the 128meg one. Could be sooo very nice for troubleshooting PCs.

 

[Mday]

the theoretical speed of flash memory is very slow relative to sustained transfer rates of a modern HDD. notice i said sustained. burst speeds significantly out do the speeds of flash memory. not to mention electron tunnelling limiting writes to about 100,000 times.

of course if you were to build a RAM drive which requires a constant power source...

 

[jonmullen]

They make a program that you can use to partition part of your system memory as a RAM drive and then you can set backup meathods. Like have it use system Idle time to write to contents of the RAM drive to the hard drive so that if you loose power you do not loose your data.

 

[Howard]

Originally posted by: Mday
the theoretical speed of flash memory is very slow relative to sustained transfer rates of a modern HDD. notice i said sustained. burst speeds significantly out do the speeds of flash memory. not to mention electron tunnelling limiting writes to about 100,000 times.

of course if you were to build a RAM drive which requires a constant power source...

34 to 230 MB/sec Sustained R/W Rate
40 to 320 MB/sec Burst R/W Rate

^ BiTMICRO's 3.5" SCSI-UW. Is the 230MB/s bogus? It's pretty high...

 

[Peter]

The RAM based drives (usually with rotating HDD in the background) are as fast as their interface allows. 320 MB/s is the peak throughput of U320 SCSI.

FlashROM drives are a lot slower, hardly faster than 4 MB/s if you're lucky, 1 MB/s if you´re not.

 

[zephyrprime]

the theoretical speed of flash memory is very slow relative to sustained transfer rates of a modern HDD. notice i said sustained. burst speeds significantly out do the speeds of flash memory. not to mention electron tunnelling limiting writes to about 100,000 times.

The speed of flash memory varies a lot. There are chips made that provide a sram latch line thus potentially giving sustained speeds of the same order as DRAM.

linky (do the math and you'll see the speed is 80MB/s with one chip)

Most flash is slow because there's no need for faster flash in digital cameras which are by far the biggest application for flash.
I've seen one company that offers multigigabyte flash drives that have 20MB/s transfer (which is really kinda slow when you think about it.)

The drives at http://www.memorydepot.biz/diskonmodule/ seem to be slower than USB flash drives.

 

[Guybrush]

Old discussion i brought up about this.

 

[Fallen Kell]

Actually one of my friends has been working with some solid state hard drives that are EXTREMELY FAST (i.e. as fast as RAM), but do not suffer from the need for constant power. The main (and only) drawback is price, its EXPENSIVE.

 

[dakels]

Originally posted by: jonmullen
They make a program that you can use to partition part of your system memory as a RAM drive and then you can set backup meathods. Like have it use system Idle time to write to contents of the RAM drive to the hard drive so that if you loose power you do not loose your data.

Mac OS has allowed for this for as long as I can remember (10-15 years ago on OS 5). Its just a "RAM disk" It allowed you to partition some of your RAM as a virtual HD. Placing your graphical or audio files in there and setting it as a scratch disk saved a humongous amount of time in the old days. Undoing a change from a file on the HD could have taken 60 seconds, but on RAM it would be 5-10 seconds (not exact figures). Nowadays the memory management is better and people working in big files are also on systems with 1-2gb RAM that will automatically preload working files into RAM. Also much faster HD's. Still, even working on a RAID 0 or RAID 5, having enough RAM for all your scratch files still goes alot faster then using virtual memory (HD).

 

[ravedave]

Dans Data has a brand new article on this.

http://dansdata.com/gz020.htm


Yay my 500th post!