[CentOS] ZFS @ centOS

Tue Apr 5 20:19:49 UTC 2011
rainer at ultra-secure.de <rainer at ultra-secure.de>

> But ...
> I've been reading about some of the issues with ZFS performance and have
> discovered that it needs a *lot* of RAM to support decent caching ...
> the recommendation is for a GByte of RAM per TByte of storage just for
> the metadata, which can add up.  Maybe cache memory starvation is one
> reason why so many disappointing test results are showing up.

Yes, it uses most of any available RAM as cache.
Newer implementations can use SSDs as a kind of 2nd-level cache ("L2-ARC").
Also, certain on-disk logs can be written out to NVRAMs directly, speeding
up things even more.
Compared with Cache-RAM in RAID-Controllers, RAM for servers is dirt-cheap.

The philosophy is: why put tiny, expensive amounts of RAM into the
RAID-controller and have it try to make guesses on what should be cached
and what not - if we can add RAM to the server directly at a fraction of
the cost and let the OS handle _everything_ short of moving the disk-heads
over the platters.

IMO, it's a brilliant concept.

Do you know if there is a lot of performance-penalty with KVM/VBox,
compared to Solaris Zones?