[linux-lvm] Can we make char files not blocked for the volumes

Stephen C. Tweedie sct at redhat.com
Tue Feb 22 17:50:42 UTC 2000


On Mon, 21 Feb 2000 16:45:06 -0600, Chris Anderson <chris at alwan.com>

>  It is odd how it is used.  I had to hack it into 2.2.14, but go it working.
> I think the "raw" command is odd, also it needs to be run every time you
> reboot.  

Indeed --- the raw interfaces need to be bound to specific devices just
as eth* network interface names need to be bound to addresses.

> Also who is the owner of this code. How does it find its way into
> the standard 2.3 and lvm has not yet?  That is odd too.

lvm just took a little longer --- they are both in 2.3 now.

> My test with Informix IDS 7.3 for linux showed that the raw io is twice as
> slow.  A 17 mins load under block device using lvm but took 31mins for the
> raw linked version.  I will be testing the Informix 9.2 version
> tonight. 

Raw IO does not do any caching in the O/S.  Specifically, it doesn't
perform any readahead or writebehind.  If the application was using
that implicit caching then raw IO will necessarily be slower.


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