Dual CPU vs more ram

[KentShades]

Currently building out a FreeNAS unit with ix systems, and would just like to know. How important is a Dual CPU socket vs say more RAM? Currently were sitting at 64GB of Ram and a Intel Quad Core 3.50Ghz Xeon 10MB cache (130W) (E5-1620v3) with about 60 TB's of Raw HD space. We'd like to do dedupe/compression with this NAS and just see what we would be the better choice for now, and in the future. I like the idea of eventually adding another CPU if it's needed to speed things up. What do you guys think?

 

[anodos]

Currently building out a FreeNAS unit with ix systems, and would just like to know. How important is a Dual CPU socket vs say more RAM? Currently were sitting at 64GB of Ram and a Intel Quad Core 3.50Ghz Xeon 10MB cache (130W) (E5-1620v3) with about 60 TB's of Raw HD space. We'd like to do dedupe/compression with this NAS and just see what we would be the better choice for now, and in the future. I like the idea of eventually adding another CPU if it's needed to speed things up. What do you guys think?

Dedup is usually a bad idea. More RAM is almost always a good idea. How are you planning to use the NAS? Without more info, I'd say get more RAM and a second CPU (it's not like they're mutually exclusive).

 

[KentShades]

Why is dedup usually a bad idea? Were planning on making this a NAS for backups for Veeam with both 9.0 and Cloud Connect.

 

[Stephen2]

I am not expert, but have read here that dedup should have approximately 5GB of RAM per 1TB of drive space... 60TB * 5 = 300GB RAM to support dedup on so much data...

Of course this might mean "data after accounting for parity & 80% full drives" which would take this down a lot, but still much higher than 64GB.

If you don't have enough RAM, I've read that it will start swapping to disk for the storage of dedup information, thereby slowing things down hugely.

 

[anodos]

Why is dedup usually a bad idea? Were planning on making this a NAS for backups for Veeam with both 9.0 and Cloud Connect.

http://doc.freenas.org/9.10/freenas_storage.html#deduplication

"Be forewarned that there is no way to undedup the data within a dataset once deduplication is enabled as disabling deduplication has NO EFFECT on existing data. The more data you write to a deduplicated dataset, the more RAM it requires and when the system starts storing the DDTs (dedup tables) on disk because they no longer fit into RAM, performance craters. Furthermore, importing an unclean pool can require between 3-5 GB of RAM per TB of deduped data, and if the system doesn’t have the needed RAM it will panic, with the only solution being to add more RAM or to recreate the pool. Think carefully before enabling dedup! This article provides a good description of the value versus cost considerations for deduplication."

 

[Stephen2]

Here:
https://doc.freenas.org/9.3/freenas_storage.html#deduplication
http://www.freenas.org/blog/freenas-worst-practices/