[mythtv-users] Compact Flash write cycles (was: Re: Intro---)

Stroller linux.luser at myrealbox.com
Sun Jan 6 14:17:25 UTC 2008

Hi David,

Many, MANY, thanks for your reply. I'm using MyRealBox for mailing  
lists at the moment, and can be really flakey with delays over email  
delivery. I'm going to change addresses Real Soon Now, but I was  
beginning to think everyone was ignoring my posting. ;)

A couple of further questions below, if I could possibly prevail upon  
you for enlightenment:

On 2 Jan 2008, at 15:43, David George wrote:
> On 01/01/2008 05:48 AM, Stroller wrote:
>> This is something I'm interested in, but haven't tried. I understood
>> that modern flash devices would handle many more writes than early  
>> ones.
> This is true.  Early flash was 100,000 writes.  Current NAND flash is
> typically 1,000,000 writes.  However this is writes to a sector
> (smallest writable unit).

I'm not entirely clear on the implications of this. Are you say that  
1,000,000 TOTAL writes will cream the flash, and that this is a lot  
less than 1,000,000 writes ON EACH SECTOR?

> The other catch is you will really want to
> use a filesystem designed specifically for wear-leveling like YAFFS.
> With 1,000,000 writes, if you write to the same sector once per  
> second,
> you get about twelve days worth of writes.
> ...
> I am not sure that compact flash devices have the built-in wear  
> leveling
> mentioned in the article.  SD may.  I haven't researched that far into
> it as we usually work with NAND flash using YAFFS in the embedded
> systems at work.

OK, so assuming we use either a device with self-levelling or an  
appropriate flash filesystem, is it ok to put the root filessystem &  
MySQL database on a CF card? Or do we still get too many writes to do  
that safely?

I see indications that YAFFS can run on a 2.6 kernel, but JFFS is  
already part of the main tree. Is JFFS wear-leveling?


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