On Sep 28, 2009, at 10:42 PM, Stefan Monnier wrote:
I have debian installed onto a 4gb usb stick (my laptops HD crashed
and i'm using this as a temporary solution till i get it fixed). All
works great. The only issue is that periodically, the whole system
will freeze for 1-3 seconds and then come back. It doesn't matter if
I'm just doing some CLI stuff or using opera for web browsing.
Happens
sporadically and seemingly at random.
What/where would I need to look on my system to possibly diagnose
this
issue?
It's a problem with the flash key (most/all flash keys suffer from
this
problem). It is also seen in many SSDs (it's a phenomenon referred to
as "stutter"). There's not much you can do about it, IIUC.
Stefan
The problem is essentially (it's actually a bit more complicated, but
essentially) that the flash RAM fills up with un-erased pages and has
to be garbage-collected. Because the flash controller doesn't know
the details of the host's file system, it uses a naive brute-force
garbage collection algorithm. Hence "stutter".
There's a protocol standards revision in the works, called TRIM, that
will allow the host to tell the flash what parts of the file system
can be erased and what it needs to keep. This will allow smarter
garbage collecting, which can happen in the background.
Flash SSDs with the TRIM feature are planned to be available in
2010. It may take a while after that for Linux to be able to use it
effectively.
I don't know what (or even "if") the time-frame will be for getting
TRIM into USB sticks.
Rick
Reference: http://www.anandtech.com/storage/showdoc.aspx?i=3631
"Understanding and Choosing the Best SSD"
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