# ZFS with only 2GB



## mefizto (Aug 30, 2013)

Greetings all,

I have acquired an older laptop (HP 2550se), with a maximum supported memory size of 2 GB.  The search, e.g. ZFS Tuning Guide, appears to suggest that no tuning is required for more than 2 GB; however, some people reported no problems with 2 GB.

What is the current status?  Will I have problems with ZFS and should, consequently, stay with UFS?

Kindest regards,

M


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## giahung (Aug 30, 2013)

I think you stay with UFS is better. I have 4 GB of RAM and am using PC-BSD 9.1 with Xfce and KDE desktop environment. The KDE System Monitor said that the system uses only 600 MB of RAM, but I see that it is really slow. So I switch to Xfce Task Manager, it said the whole system (with no other applications running) uses about 2700 MB of RAM! And if I am copying or moving files it eats about 3270 MB of RAM. I installed PC-BSD with default options.

Sorry about my English.


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## wblock@ (Aug 30, 2013)

Appearances can be misleading: Why does top show very little free memory even when I have very few programs running?


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## SirDice (Aug 30, 2013)

My old server only had 2 GB and it ran ZFS just fine. Stay away from stuff like dedup though. Normal usage and even some compression shouldn't be a problem.


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## jem (Aug 30, 2013)

My co-located server has been running just fine with ZFS and only 2 GB of RAM for over four years, without any tuning.  It has a single mirrored pool with about 20 datasets.


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## kpa (Aug 30, 2013)

Limit the ARC cache manually to something like 512-768 MB. Otherwise you'll run a risk of kernel memory exhaustion.


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## SirDice (Aug 30, 2013)

kpa said:
			
		

> Limit the ARC cache manually to something like 512MB-768MBs. Otherwise you'll run a risk of kernel memory exhaustion.



I never tweaked anything to be honest. And I had been using tmpfs(5), building packages and running a large Java application at the same time. I never had any memory issues. Even it's swap barely got used. I did have some swap usage but that was caused by the Java application. If I didn't run that no swap would be used.


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## kpa (Aug 30, 2013)

I meant that you should leave enough memory for applications and other parts of the kernel. Depending on the use you could up the ARC cache as high as 1.5 GB roughly, for example if the server is a pure file server. The numbers I gave are safe and conservative ones for a machine that might be used as a desktop/laptop.

Autotuning may work or may not with 2 GB, the magic number seems to be around 4 GB of physical memory after which the autotuning usually does a good job of setting reasonable defaults.


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## mefizto (Aug 30, 2013)

Gentlemen,

Thank you for the replies. Based on them, I intend to use ZFS, my main motivation being snapshots, with no tuning, and ask for help if the kernel memory exhaustion problem appears.

Kindest regards,

M

P.S. How do I mark the thread "Solved"?

M


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## fonz (Sep 4, 2013)

mefizto said:
			
		

> P.S. How do I mark the thread "Solved"?


http://forums.freebsd.org/showthread.php?t=38472


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