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Old 08-28-2011, 03:19 PM
Scott Ferguson
 
Default A Question about Journalling File Systems and Flash Drives

On 29/08/11 00:03, green wrote:

Scott Ferguson wrote at 2011-08-27 08:50 -0500:

I don't imagine upgrading will make much difference - the controller
distributes the writes evenly, for which reason I reserve 25% of
space when installing (instead of the default 10%). NOTE: I could be
wrong about that - I'm just guessing.


Hmm, that reserves 25% for root use only, something that occurs above the
filesystem level.


Is that a specific area that's reserved - or just an amount of space
kept free for root?



So probably you are giving up 25% of the space
and gaining nothing.


In this instance the install used is less than 300MB, and it's unusual
for me to have more than 1GB on the stick - so I'm not giving up
anything. The stick is used to move my configs and an OS, not to ferry
data - I use the tubes for that.



And the default is 5% according to mke2fs(8).


That would be a guessing I warned of. ;-p

Currently I use ext3 which has (major) fragmentation problems when it
runs short on space (90-95% of space) - especially when used for lots of
frequent, small writes as it is. My concern was/is that fragmentation
would shorten the lifespan - another reason to move to ext4.


NOTE: when I first created the sticks I was expecting 6 month lifetimes
based on the pessimistic estimates people were making at the time. It
was only later I realised those estimates didn't allow for how the
controllers distribute writes.



Cheers


--
"You ever noticed how people who believe in Creationism look really
unevolved? You ever noticed that? Eyes real close together, eyebrow
ridges, big furry hands and feet. "I believe God created me in one day"
Yeah, looks liked He rushed it."

— Bill Hicks


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Old 08-28-2011, 09:00 PM
green
 
Default A Question about Journalling File Systems and Flash Drives

Scott Ferguson wrote at 2011-08-28 10:19 -0500:
> On 29/08/11 00:03, green wrote:
> > Scott Ferguson wrote at 2011-08-27 08:50 -0500:
> > > I don't imagine upgrading will make much difference - the controller
> > > distributes the writes evenly, for which reason I reserve 25% of
> > > space when installing (instead of the default 10%). NOTE: I could be
> > > wrong about that - I'm just guessing.
> >
> > Hmm, that reserves 25% for root use only, something that occurs above the
> > filesystem level.
>
> Is that a specific area that's reserved - or just an amount of space
> kept free for root?

mke2fs(8):
"percentage of the filesystem blocks"

I read that as just an amount of space reserved so that if a regular user
fills up the filesystem, he is denied further writes while root processes can
still write.

> Currently I use ext3 which has (major) fragmentation problems when
> it runs short on space (90-95% of space) - especially when used for
> lots of frequent, small writes as it is.

mke2fs(8) does mention using a reserved-blocks-percentage to reduce
fragmentation. But it only limits user processes.
 
Old 08-28-2011, 10:49 PM
green
 
Default A Question about Journalling File Systems and Flash Drives

Brad Alexander wrote at 2011-08-26 16:49 -0500:
> card slot on his brand new win7 laptop...and grabbed her card and Windows
> partially formatted (corrupted) it.

> Since that 8GB card was broken, she upgraded to a 16GB card

Can Windows really *break* a card (rather than just the filesystem on it)?
 
Old 08-29-2011, 01:54 AM
Scott Ferguson
 
Default A Question about Journalling File Systems and Flash Drives

On 29/08/11 07:00, green wrote:

Scott Ferguson wrote at 2011-08-28 10:19 -0500:

On 29/08/11 00:03, green wrote:

Scott Ferguson wrote at 2011-08-27 08:50 -0500:

I don't imagine upgrading will make much difference - the controller
distributes the writes evenly, for which reason I reserve 25% of
space when installing (instead of the default 10%). NOTE: I could be
wrong about that - I'm just guessing.


Hmm, that reserves 25% for root use only, something that occurs above the
filesystem level.


Is that a specific area that's reserved - or just an amount of space
kept free for root?


mke2fs(8):
"percentage of the filesystem blocks"

I read that as just an amount of space reserved so that if a regular user
fills up the filesystem, he is denied further writes while root processes can
still write.


Which was roughly my interpretation - a certain amount of shuffle space
is left which isn't used by user processes, but can at any given time be
any areas of the filesystem.


If I get a chance I'll dig up the paper written earlier this year about
SSD write controller, from foggy memory it was a local research effort -
upset the forensics experts at the time, and goes into detail about how
the controllers actually present the system.(which is completely
different to how conventional physical drives do things).


Sorry, brain not working today, very late night battling cPanel
limitations and SSL problems.





Currently I use ext3 which has (major) fragmentation problems when
it runs short on space (90-95% of space) - especially when used for
lots of frequent, small writes as it is.


mke2fs(8) does mention using a reserved-blocks-percentage to reduce
fragmentation. But it only limits user processes.


From my original notes - I based that on a post by Theodore "Ted" Ts'o,
(ext3 redhat list?), end of Jan '09 (I've got the original post
somewhere... damn Strigi!) - it's possible he didn't put everything into
the man.

At least I now know how long the stick in question has seen daily use.

Cheers

--
"I've got a bathtub and an imagination, I'm staying indoors this summer.
That way I can listen to music that I like."
— Bill Hicks


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Old 08-29-2011, 02:24 AM
Scott Ferguson
 
Default A Question about Journalling File Systems and Flash Drives

On 29/08/11 08:49, green wrote:

Brad Alexander wrote at 2011-08-26 16:49 -0500:

card slot on his brand new win7 laptop...and grabbed her card and Windows
partially formatted (corrupted) it.



Since that 8GB card was broken, she upgraded to a 16GB card


Can Windows really *break* a card (rather than just the filesystem on it)?


It 'might' be an urban myth - I've heard it often but most instances I
came across were recoverable (parted), some where not.
Disclaimer: my experience of that problem is very limited - maybe half a
dozen instances.
I "suspect" the problem stems from autoformat, and a problem with
Sdbus.sys during ADMA tranfers - MS pushed out some updates in late '09
that seemed to fix it. NOTE: It only seemed to occur with un-updated
laptops - so I'm not certain that heat didn't play a part.


Cheers

--
"I've got a bathtub and an imagination, I'm staying indoors this summer.
That way I can listen to music that I like."
— Bill Hicks


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Old 10-29-2011, 08:59 AM
Andrei Popescu
 
Default A Question about Journalling File Systems and Flash Drives

On Sb, 27 aug 11, 19:39:33, Rob Owens wrote:
>
> I recall reading that ext4 is much quicker than ext3 on flash drives, so
> you may want to consider using that. Although I'm not sure what you
> have to do to get Lenny to support ext4.

Done that: the minimum would be backported kernel + e2fsprogs. If you
use tools that deal with filesystems directly you need to check their
compatibility as well.

Kind regards,
Andrei
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