How much memory do I need?

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Jay-Hawks

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This is my first post on the FreeNAS forum so I would qualify as NOOB. I have done a lot of reading and I have learned a lot but I have one question regarding memory that I haven't been able to find. I was planning on running a RAID5 setup before I started reading but learned that the RAID-Z1 (RAID5) was NOT recommended so I'm now planning on a RAID-Z2 configuration. My plan is to initially start with 5 drives (4TB each) in a RAID-Z2 configuration and everything that I have read says that I need 1 GB of memory for every 1 TB of storage in a ZFS file system but my question does that apply to the total usable space of the VDev or the total space of all the drives in the VDev? So in my case I would have a total of 20TB with all 5 drives but only 12TB of usable space. The question is are my memory needs based on the 12TB or 20TB?

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Chris Moore

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Above the 8MB minimum it's fuzzy, and it depends on the kind of performance and workload you expect to get from your pool. Depending on what you're doing 16 GB of RAM is probably an adequate configuration.

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Jay-Hawks

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Above the 8MB minimum it's fuzzy, and it depends on the kind of performance and workload you expect to get from your pool. Depending on what you're doing 16 GB of RAM is probably an adequate configuration.

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Sorry I should have given a little more detail. My system will have two primary functions. First it will serve a data storage for family pictures and videos that if I lost my wife would divorce me.

Second, I will use is as a plex server. Initially I'm thinking that I want it to be able to do three transcode streams at once even though I don't see me ever needed that many. Most of the time when we watch plex it's either on the home network (no transcoding) or on a portable device with the video file having been transcoded and downloaded to the portable device.
 

Chris Moore

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Sorry I should have given a little more detail. My system will have two primary functions. First it will serve a data storage for family pictures and videos that if I lost my wife would divorce me.

Second, I will use is as a plex server. Initially I'm thinking that I want it to be able to do three transcode streams at once even though I don't see me ever needed that many. Most of the time when we watch plex it's either on the home network (no transcoding) or on a portable device with the video file having been transcoded and downloaded to the portable device.
I ran my Plex on system with 16 gigs of RAM for a couple years and it worked fine. Last year, I upgraded to 32 gigs and don't really see a big performance difference. You should be good with either of these.

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danb35

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I agree with @Chris Moore that 16 GB will probably be fine--the rule of thumb you cite is very rough and deliberately vague. But when you're buying your hardware, leave room to expand the RAM in case it's necessary in the future.
 
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