At 11:05 PM -0700 2000/4/26, Matthew Dillon wrote:
> You should be able to create a large virtual VN device. man
> vnconfig for more information - you have the choice of making it
> file-backed, swap-backed, or swap-backed with the swap pre-reserved.
> file-backed VN devices have a sector size of 512 bytes (which is
> standard). Swap-backed VN devices have a sector size of a page (4K on
> PC's).
Hmm. This has got me thinking....
I use a mfs for storing the Diablo history file on our news
peering server. Yes, I know the front part of the file is mmap()'ed
and effectively kept completely in memory anyway, but I've seen
periods of time when we received over 160,000 articles in a single
hour (an average of about 45 per second), and if you compare this to
our normal ratio of offered versus accepted articles (something in
the range of 32,238,303 vs. 612,429; for a 52.64:1 ratio), this would
imply we probably did something like 2,368.8 history lookups per
second during that period of time -- and this is just for inbound
articles.
In my experience, it is a non-trivial exercise to build a drive
array system that can keep up with the number of disk accesses
necessary to handle this many history lookups per second. I think
I've recently done it (and reported my testing results on
news.software.nntp, along with summarizing the previous test results
from Joe Greco and Terry Kennedy), but it's still non-trivial and the
solutions I've seen so far are all still rather expensive. Thus the
reason why I currently continue to use an mfs for the history
database.
However, now I'm wondering if it might not be better to use a
file-backed or maybe a swap-backed VN device instead of an mfs. Do
you have any thoughts?
--
These are my opinions -- not to be taken as official Skynet policy
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