Many thanks Andrew for the info :-)

Best regards,

Kaya


On 02/01/10 12:29, andrew wrote:
See comments inline below:


You can limit the amount of memory that ZFS uses
for its cache (the ARC - Adaptive Replacement Cache)
as described here:

http://www.solarisinternals.com/wiki/index.php/ZFS_Evi
l_Tuning_Guide#Limiting_the_ARC_Cache
In fact the live CD does just that in order to
allow OpenSolaris to install on systems with only
512MB memory - check /etc/system while booted from
the live CD to see what it is set to.
Cheers

Andrew.

Hi, I do NOT wish to hijack this thread but have a
question related to this
answer:

what is the advantage or disadvantage of limited the
ZFS cache???
Read the page I linked to.

Additionally does it depend on system size; ie. how
large the - and how
many hard disks there are??
The *maximum* ARC size is based on the total amount of RAM in the system if I 
recall correctly. It will default to 7/8ths of available RAM, or RAM minus 1G - 
whichever is greater. It starts of small but gets bigger as more stuff is read 
off disk. The ARC is shared between all ZFS pools and filesystems which you 
have active on the system - again see the page I linked to for more details.

So say for a system with 2GB memory if the app +
kernel + background
procs takes up 1.5GB then if one limits the ZFS cache
to 512MB what
significance does this have??
It means your background processes get less of a hard time from the ARC cache 
as they fight for memory, since the ARC will not attempt to grow beyond 512MB. 
You will probably want to have a play with it and see what the effect is on 
your actual system - it may take a bit of trial and error to get the right 
setting for your particular circumstances.

Regards and apologies for the intrusion!!

Not a problem ;-)

Andrew.
Kaya
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