[PortableFirefox] a couple of questions

[John T. Haller]

Matthew Weymar wrote:

> http://en.wikipedia.org/wiki/Keydrive#Strengths_and_weaknesses addresses 
> some of my concerns / curiosity in the following:
> 
> "In normal use, mid-range flash drives currently on the market will 
> support several million cycles, although write operations will gradually 
> slow as the device ages. This should be a consideration when using a 
> flash drive as a hard drive to run application software or an operating 
> system."
> 
> (This comment is followed by an oblique reference to the Portable 
> Firefox project: "To address this (and the space limitations common on 
> flash drives) some developers have produced versions of operating 
> systems (such as Linux <http://en.wikipedia.org/wiki/Linux>) or 
> commonplace applications (such as the Mozilla Firefox 
> <http://en.wikipedia.org/wiki/Mozilla_Firefox>) designed to run from 
> flash drives." Perhaps this ref. should be less oblique!)

Portable Firefox is mentioned within the Wikipedia Firefox entry (thanks 
to a PFF fan).

> In any case, this info is only so helpful, as I am a bit stuck as to how 
> to estimate the number of "cycles," or "write cycles" various setups 
> would generate.
> 
> I notice, e.g., that you disable Browser History, and Disk Cache. I'm 
> wondering how many cycles this will save me, for example? Obviously it 
> depends on my browsing habits, which I guess I can measure / estimate 
> using my browser history(!)
> 
> Should I assume 1 write to History, and 1 write to Cache = 2 cycles per 
> URL in my history?... (Not sure how cache works exactly - nor revisiting 
> 'sites, nor 'sites that update automatically.)

Nope.  Very different.  Here are some considerations in terms of write 
cycles...

1. AFAIK, when taking about write cycles, we're talking per sector.  So, 
a file taking up 8 sectors would cause one write per sector to 8 
different sectors.

2. Some keys distribute writes evenly over the entire area, some do not 
(and none seem to mention this in their specs).  The ones that 
distribute will last longer.  The ones that do not will overuse certain 
sectors eventually.

3. As for history, each image, css, html, js, etc file will be written 
to your cache.  Each will cause 1 write per sector over however many 
sectors they take up.  So, you can see lots of writes per webpage visit.

4. Disabling things like history keeps the size of the install of PFF 
down (which is more important to some than others)

5. Disabling things like history, cookies, etc actually makes PFF faster 
over USB 1.1 (since writing and reading is so slow)

> Ultimately, I would be curious to know: How much money am I saving 
> here?... Or is that not the right rubric at all?... I take it that the 
> point is to prolong the life of my device - so I don't have to go out 
> buy another one - and so I'm trying to figure out by how long I will be 
> able to prolong it by making certain sacrifices, obviously so that I can 
> figure out which sacrifices I do and don't want to make.

In the end, it's up to you.  And it is kinda a coin flip in some ways. 
Personally, I think it makes more sense to keep the settings.

> Assuming I'm not the *only* one - though there may not be many - who is 
> similarly curious, and similarly clueless, it occurs to me that you 
> might want to add something on this subject to your Portable Firefox 
> page <http://johnhaller.com/jh/mozilla/portable_firefox/>. E.g., "For 
> more on the limited lifespans of USB key drives, check out 
> http://en.wikipedia.org/wiki/Keydrive#Strengths_and_weaknesses," or 
> paraphrase this yourself.

Actually, you're the only one to ever ask in detail.  Most folks are 
aware of the limited life span of flash memory.  And those that aren't 
never ask past "why is this disabled".

Regards,
John