ZFS : Can arc size value exceed Physical RAM ?


 
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Operating Systems Solaris ZFS : Can arc size value exceed Physical RAM ?
# 1  
Old 10-09-2012
ZFS : Can arc size value exceed Physical RAM ?

Hi,
kstat -p -m zfs -n arcstats -s size returns
zfs:0:arcstats:size 8177310584
this values is approx (7.61 GB)

but my Physical Memory size is only 6144 Megabytes.

Can this happen ?
if yes, then how can I find free memory on the system.

BTW, I ran the kstat commands from a Non global zone.
# 2  
Old 10-10-2012
Before VM, free memory was gold, but in VM it is an accident of exiting programs. RAM may be unfreed but instantly available, mapped but unmodified relative to the backing disk. You need more RAM if you cannot tune the apps and data to run with what you have fast enough. VM apps with dynamic libs share RAM, for instance. A reduces variety of apps on a system releases memory. If the apps on a specific server work on a subset of all data, that reduces RAM churn.
# 3  
Old 10-11-2012
Quote:
Originally Posted by sapre_amit
kstat -p -m zfs -n arcstats -s size returns
zfs:0:arcstats:size 8177310584
this values is approx (7.61 GB) but my Physical Memory size is only 6144 Megabytes.

Can this happen ?
If your NGZ physical memory is capped, this can indeed happen. kernel memory is shared by all zones so is not restricted by capping.
What says, from the global zone:
Code:
echo ::memstat | mdb -k

?
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