On Mon, 15 Jun 2009, Bob Friesenhahn wrote:
On Mon, 15 Jun 2009, Thommy M. wrote:
In most cases compression is not desireable. It consumes CPU and
results in uneven system performance.
IIRC there was a blog about I/O performance with ZFS stating that it was
faster with compression ON as it didn't have to wait for so much data
from the disks and that the CPU was fast at unpacking data. But sure, it
uses more CPU (and probably memory).
I'll believe this when I see it. :-)
With really slow disks and a fast CPU it is possible that reading data the
first time is faster. However, Solaris is really good at caching data so any
often-accessed data is highly likely to be cached and therefore read just one
time. The main point of using compression for the root pool would be so that
the OS can fit on an abnormally small device such as a FLASH disk. I would
use it for a read-mostly device or an archive (backup) device.
Well, it depends on your working set and how much memory you have.
I came across systems with lots of CPU left to spare but a working set is
much bigger than the amount of memory and enabling lzjb gave over 2x
compression ratio and make an application to run faster.
Seen it with ldap, mysql and couple of other apps.
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