Use of memory card for caching?

Marcus Bointon marcus at
Sun Feb 11 10:34:32 UTC 2007

On 10 Feb 2007, at 23:12, Ask Bjørn Hansen wrote:

> I thought the main advantage was that reading from a flash cards  
> takes less battery in a laptop/ipod/phone/....  They aren't  
> particularly fast compared to a hard drive and still insanely slow  
> compared to real memory.

A good flash drive will sustain about 18Mb/sec, most cheap ones are  
around 6. One big advantage they have is extremely low and consistent  
latency, usually below 1ms, which is way faster than HDs, so for  
small amounts of data they could be pretty good.

RAM will always be much faster.

> Also: Consumer flash cards have a very limited number of write  
> cycles before they burn out.  "Industrial" cards are much better,  
> but at least in low quantities they are quite expensive (relatively).

I know that drives used to have bad write cycle limits, but I also  
know that this has risen dramatically in recent years - I'm pretty  
sure I've seen >1m cycles mentioned. Most use wear levelling to  
reduce the effects of this. However, it's still something to be wary of.

Personally I think they make an excellent local backup resource,  
taking so little space and power that there's no excuse not to have  
one plugged into every server.

Marcus Bointon
Synchromedia Limited: Creators of
marcus at |

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