Freenas - do I need SSD cache?

[Gerr]

I am building a FreeNas server that will have multiple roles.  Based on my hardware and the zpool roles, would any of the zpools benefit from an SSD cache, ZIL and/or L2ARC, and how big?  Or would bumping the RAM from 16gb to 32GB(max) be better?

 

Server hardware...

Xeon E3-1226v3 CPU

16GB ECC DDR3-1600 RAM

2x Intel i210 NIC's teamed (my switch supports this)

SeaSonic 450W Gold PSU

Fractal Design Define R4 case

 

zpool #1 - Plex media

3x 3TB HGST NAS drives in RaidZ1.

*storage of movies, Plex server itself will be on a dedicated SSD.

 

zpool #2 - NAS

2x 3TB WD Red NAS drives, mirrored.

*Windows Server will remap home drives to this location.

 

zpool #3 - Backups

2x 4TB HGST drives, mirrored.

*client backup of all PC's on my home network.

 

zpool #4 - Wife's Mac NAS

2x 1TB WD Red NAS drives, mirrored.

*dedicated storage for my wife's Mac, mainly photo storage as photography is her hobby.

 

 

Would any of these zpools benefit from a 32GB/64GB/128GB SSD ZIL and/or L2ARC cache?  And how would that compare maxing out the RAM?

[Mikensan]

Nothing there looks like a demanding use case, and without a 10gb NIC card you'll never use a cache. Order of upgrades would normally be RAM and then cache.

 

It's not the pool but the demand that would call for cache. Majority of home users will not have a need for cache.

[Gerr]

I would probably have a max of 3 Plex streams, which is the only zpool that would get hit with multiple requests at the same time.

[AshleyAshes]

9 hours ago, Gerr said:

I would probably have a max of 3 Plex streams, which is the only zpool that would get hit with multiple requests at the same time.

Reading three media files concurrently, even full remuxed blu-rays, would be a trivial task for any NAS and you don't need to any special storage solutions for it.  Even a simple external HDD on USB3 could handle 10+ full remuxed BDs concurrently without issues.

 

If Plex is transcoding, there's a factor of CPU demand, but that would vary depending on what content must be decoded and then what it needs to be transcoded to.  But yeah, storage is not a concern.

[Gerr]

CPU will be a Xeon E3-1226V3, so a Haswell i5 equiv, which is plenty powerful enough for that.

 

I do have a spare 64GB MLC SSD, so was thinking I could use it as a cache somewhere.

[dalekphalm]

21 hours ago, Gerr said:

I am building a FreeNas server that will have multiple roles.  Based on my hardware and the zpool roles, would any of the zpools benefit from an SSD cache, ZIL and/or L2ARC, and how big?  Or would bumping the RAM from 16gb to 32GB(max) be better?

 

Server hardware...

Xeon E3-1226v3 CPU

16GB ECC DDR3-1600 RAM

2x Intel i210 NIC's teamed (my switch supports this)

SeaSonic 450W Gold PSU

Fractal Design Define R4 case

 

zpool #1 - Plex media

3x 3TB HGST NAS drives in RaidZ1.

*storage of movies, Plex server itself will be on a dedicated SSD.

 

zpool #2 - NAS

2x 3TB WD Red NAS drives, mirrored.

*Windows Server will remap home drives to this location.

 

zpool #3 - Backups

2x 4TB HGST drives, mirrored.

*client backup of all PC's on my home network.

 

zpool #4 - Wife's Mac NAS

2x 1TB WD Red NAS drives, mirrored.

*dedicated storage for my wife's Mac, mainly photo storage as photography is her hobby.

 

 

Would any of these zpools benefit from a 32GB/64GB/128GB SSD ZIL and/or L2ARC cache?  And how would that compare maxing out the RAM?

While more important for Parity based pools, keep in mind the ZFS rule of thumb is:

8GB RAM Minimum

1GB of RAM for every 1TB of storage

 

You have ~25TB of storage, total. If possible, I would increase your RAM from 16GB to a minimum of 24GB - or even 32GB (Won't need the extra, but it might be a similar cost).

 

I really don't think you need an SSD cache of any kind. Would it help? Sure it would make things faster under certain circumstances, but I don't see any particular usage you've stated that will highly benefit.

 

Another thing to consider:

You've got 9 HDD's listed (10 if you count the "dedicated SSD for Plex" - 11 if you're also using a separate drive for the OS itself).

 

The Define R4 supports 8x 3.5" HDD's out of the box, plus 2x 2.5" drives. So the SSD is fine, but you can't fit all 9 HDD's without looking at other solutions. Now, the Define R4 does have 2x 5.25" bays, so you could simply use a couple of 5.25"-to-3.5" bracket adapters, or a dual-5.25" bay converter (Which will usually give you 3 or 4 3.5" slots).

 

Just making sure you've considered these aspects.

[Gerr]

I already have an iStarUSA 2x5.25" to 3x3.5" hot swap adapter installed giving me 11 total 3.5" bays, plus the R4 has 2 spots behind the motherboard panel for 2.5" drives.  I also have PSU cable splitters as my PSU doesn't have enough either.  So yes, I am prepared.

 

I thought the 1GB ram for every TB of storage requirement was disproven by FreeNAS people themselves, much like ECC RAM being required.  Yes, both would be optimal, but neither are required.  Plus isn't that 1GB for 1TB only for when you use deduplication?

[dalekphalm]

1 minute ago, Gerr said:

I already have an iStarUSA 2x5.25" to 3x3.5" hot swap adapter installed giving me 11 total 3.5" bays, plus the R4 has 2 spots behind the motherboard panel for 2.5" drives.  I also have PSU cable splitters as my PSU doesn't have enough either.  So yes, I am prepared.

 

I thought the 1GB ram for every TB of storage requirement was disproven by FreeNAS people themselves, much like ECC RAM being required.  Yes, both would be optimal, but neither are required.  Plus isn't that 1GB for 1TB only for when you use deduplication?

It's not strictly required for Deduplication only. As said, it's a rule of thumb, not a law. Any parity calculations will also benefit from the increased RAM.

 

Mirrored pools likely won't see any benefit at all beyond a base amount of RAM though.

 

Many people do run FreeNAS with less than the "optimal" amount of RAM. I personally have an 18TB RAIDZ1 pool running on 12GB of RAM (though I do have an additional 8GB on it's way). I see pretty good performance. I'm actually going to compare before and after to see if the additional RAM even makes a difference (In my scenario, it might not).

 

ECC again, not required. But a "nice to have". But as was discussed in another thread, random single-bit RAM errors are super SUPER rare. Like you might encounter one error after 1.5 years kind of rare. And a single bit-flip error may not even cause issues. Depends on the specific file. A bit-flip in a JPEG, you might not even notice, for example, because it's already a "lossy" file format.

 

The 16GB of RAM you've got already is probably enough. Just wanted to make sure you've considered that angle.

[Mikensan]

While there are other advantages supposedly for more RAM, one of the advantages is it acts as buffer for file transfers. One of the fixes for slow transfers is increase RAM, but once you saturate your ethernet connection - not much to gain.