ZFS - RAM Optimization

402blownstroker

[H]ard|DCer of the Month - Nov. 2012
Joined
Jan 5, 2006
Messages
3,203
What would be better for a ZFS pool configuration?

1) building a ramdisk and adding that to the pool as cache
2) letting the zfs app take up and manage the same amount of ram
 

spankit

Limp Gawd
Joined
Oct 18, 2010
Messages
262
Assuming you are referring to read cache, making a ram disk is pretty much pointless because the memory is already being used as such (ARC). You would be over complicating things for nothing. Someone can probably elaborate on this but I would recommend doing a few google searches, there are some great articles that explain how each different form of cache works in ZFS.
 

Jim G

Limp Gawd
Joined
Jun 2, 2011
Messages
221
As spankit has said, ZFS manages RAM extremely well with regard to using it as an adative read cache (ARC); adding a RAMdisk is adding an unnecessary layer. Using a RAMdisk as L2ARC will also reduce the amount of ARC available as L2ARC eats up a small amount of RAM which would otherwise be used as cache... so you'll end up with more complexity and less RAMA available for caching.
 

Dark Shade

[H]ard|Gawd
Joined
May 2, 2006
Messages
1,872
From what I understand, just throw more RAM at it, and if you can't, adding a fast SSD for L2ARC can be beneficial. A RAMDisk would overcomplicate and actually hinder performance
 

spazoid

Limp Gawd
Joined
Jun 16, 2008
Messages
289
The fact that you're even considering this as an option, makes me think that you have a lot of reading to do before you build a ZFS box.
 
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