iscsi target buffer usage

[Oleksandr Mishchenko]

Hi!
When I used target module in CentOS 7 I can see:
Target service has total cache 2GB by default:
# cat /sys/module/target_core_user/parameters/global_max_data_area_mb
2048

How I can check this buffer usage?
I need to know: is it full or not.

Thanks.

 

[kc1di]

Hello @Oleksandr Mishchenko,
Welcome to Linux.org forum.
this terminal command will work for you.

sudo bash -c 'echo 3 > /proc/sys/vm/drop_caches && sleep 2 && free'

 

[Oleksandr Mishchenko]

This command will clean some caches. I need not clean any cache.
I need only get info how it is utilized.
That needs me to understand how much cache I need to use on this storage. Huge cache is good, but if server fails huge data will be lost...(((

 

[kc1di]

This command will clean some caches. I need not clean any cache.
I need only get info how it is utilized.
That needs me to understand how much cache I need to use on this storage. Huge cache is good, but if server fails huge data will be lost...(((

did you try the command in a terminal that I posted in my last post?

 

[Oleksandr Mishchenko]

No. Because command
echo 3 > /proc/sys/vm/drop_caches will to free slab objects and pagecache

Use of this file can cause performance problems. Since it discards cached
objects, it may cost a significant amount of I/O and CPU to recreate the
dropped objects, especially if they were under heavy use. Because of this,
use outside of a testing or debugging environment is not recommended.
(c) https://www.kernel.org/doc/Documentation/sysctl/vm.txt

My storage is under heavy use.
I need only monitoring target cache utilization.