Memory issue in Solaris

Memory issue in Solaris 

Currently server has total 327 Gb

sapdev:# echo ::memstat | mdb -k
Page Summary Pages MB %Tot
Kernel 6332481 49472 15%
ZFS File Data 19994158 156204 48%
Anon 12921795 100951 31%
Exec and libs 578486 4519 1%
Page cache 1068169 8345 3%
Free (cachelist) 101826 795 0%
Free (freelist) 946125 7391 2%
Total 41943040 327680—————-> Total Memory
Thx !!

sapdev:# prtconf | grep Mem
Memory size: 327680 Megabytes

We see that ZFS is using more physical memory on this server. We have to cap this usage and it requires a reboot of the server.

Looks like this host was using UFS for data filesystems earlier and ZFS ARC limit was not there in place.

Since FS’s are migrated to ZFS , ARC cache limit is mandatory.
Limit the ZFS ARC cache to 4GB. Otherwise ZFS consumes the vast majority of memory
which makes looking at resource consumption difficult.

we need to do the setting in /etc/system file .

set zfs:zfs_arc_max=4294967296

sapdev#

It is capped till 4Gb as per standard.It will be applied when the server re-reads /etc/system during boot.

So we need a reboot.

ZFS arc is a ZFS file system factor, which is necessary for better performance , especially for DB hosted systems.
But it grows in memory with the ZFS file system usage.
As the sap server exclusively use zfs, the arc usage is very high, which will ultimately consume all the RSS and do a performance bottleneck.

4 GB arc is a suitable size if we consider performance and RSS availability.

sapdev:# sar -r 5 5

SunOS sapdev 5.10 Generic_150400-38 sun4u 12/22/2016

13:57:40 freemem freeswap
13:57:45 16326755 693435562
13:57:50 16326117 693424515
13:57:55 16325316 693411808
13:58:00 16324695 693404640
13:58:05 16325036 693416429

Average 16325584 693418591

Note : Above sizes are given in Block , hence please convert it in MB/GB.

sapdev:# echo ::memstat|mdb -k
Page Summary Pages MB %Tot
———— —————- —————- —-
Kernel 2578688 20146 6%
ZFS File Data 467305 3650 1%
Anon 19701001 153914 47%
Exec and libs 574865 4491 1%
Page cache 2308486 18035 5%
Free (cachelist) 1095285 8556 3%
Free (freelist) 15217410 118886 36%
Total 41943040 327680
sapdev:#

Note : Above values are given in KB , Hence please convert in MB/GB.

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