Re: [9fans] Survey: Current Fossil+venti Filesystem

[ron minnich <rminnich@gmail.com>]

On Thu, Jun 23, 2011 at 9:19 AM, erik quanstrom <quanstro@quanstro.net> wrote:

> i don't think this paper applies to write-once systems like
> venti (or ken fs for that matter).

but it might apply to fossil.

> also, good ssds are rated in terms of a minimum amount of data
> that can be written to them.  an very good ssds have a minimum
> write number that means they can be written to at maximum speed
> for the drive's full rated lifetime.


The main point I took from the talk they gave was that failure was
most strongly related to the number of writes in FLASH. If your
striping strategy is to duplicate writes to each drive, you faced the
happy prospect of doing a write and having both drives fail at the
same time. Hard drives have a different way of failing. We've seen
weirdness like this here, with drives in a bunch of nodes that all
seem to fail simultaneously, well within rated lifetime. Not cheap
drives either. Of course that was a little while ago and things seem
to have gotten better, but it's worth a warning.

Anyway, it's important to keep in mind that SSDs are a bit different.

ron