Using L2ARC on freenas - is it worth it?

Hey guys, I was thinking with now SSD prices being so cheap, I could pick up 120gb SSDs for around £15 quid each.

I was debating if to get 2x 120gb SSDs for L2ARC just to play around with but I’m thinking will I actually benefit at all in doing this?

If it helps here is my current setup on freenas, i5(3470) with 16gb of ram, my storage array looks like this, 2x 500gb 2x 640gb drives, in a raidz1 and also a single 10tb drive in its own storage pool.

my network is only 1gbps I want to maybe upgrade to 10gbps however with my h200 in the nas, I don’t have any free PCI slots as my H200 rests in the only PCI slot on the motherboard.

Thanks, Leprejohn

L2ARC can help but it depends on if your workload consists the server being asked for the same data all the time.

I’m guessing you’re using DDR3 RAM. That’s also quite cheap on eBay right now since everyone is upgrading to DDR4. You might get more value out of maxing out your RAM.

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You can’t upgrade to ddr4 from ddr3 without a complete base system change. It’s a bit misleading to suggest that imho.

Ram prices across the board have dropped to sane levels, and it’s thankfully no longer the costliest thing in the cart. Last month I bought, new retail, 128gb ddr4 for $480, a far cry from what it used to be not long ago.

More to @leprejohn, it seems you’ve got a 1.5TB RaidZ1, 16GB memory is plenty sufficient for that, even using twice the guideline 1GB/1TB rule. As Tom suggests, it’s load dependent. Is your base workload less that 14GB? If so, don’t worry at all. If it’s 30GB or less, buy RAM. If it’s more than that, then consider adding an L2ARC. If it’s a pure storage server, then don’t worry at all about it as you won’t really gain anything. You’re better off investing in faster array drives.

my 2 shillings

@faust What I meant was that people are selling lots of DDR3 cheap because they are buying new systems. Not that you can put DDR4 in a DDR3 system.

The 10TB drive in the host is used for plex so sometimes the data on there is used alot, I have some shares setup for backups of files, veeam, ISO share so these tend to get used a bit at times.

The motherboard I’ve got only supports max of 16gb ram so it’s already maxed

Thanks Faust to be honest I was thinking of getting some SSD storage for some VMs and have 2 SSD in a strip just to host virtual hard disks, however I was thinking would these two SSDs be better as a cache for the array.

I’m thinking of maybe upgrading the drives for either some Toshiba P300 3TB - HDWD130UZSVA, I did see an offer for some WD 4TB reds at £96 or maybe some ironwolf drives.

To be honest I’m debating if it’s worth waiting for the 10TB Mybooks to come on sale again and get two of them so I can create a raid z1 array

The other thing to keep in mind is that you can only assign the L2ARC to a single storage pool. There is probably a way to split a ssd into multiple logical drives, but I don’t think that’s officially supported.

From personal experience, I prefer an OS pool on ssd vs using them for L2ARC and SLOG. Day to day it works well, but the spinning disks choke when trying to boot several VMs at a time. I would have to wait for about 15 minutes to get all my VMs back up after a reboot of FreeNAS.

There’s not a right or wrong answer here. You just have to weigh the pros and cons for your use case.

If VM’s are your use case, you’re probably better off using the SSD’s in an array where overall speed will win out.

I will never buy Seagate drives again, they have the worst reliability imho. The WD Reds are slower rpm drives, and I doubt they’ll ever discount the MyBooks again considering it’s known that they contain WD Red drives. The Internet & YT screwed that for everyone. As WD killed Hitachi (my longtime favorite), Toshiba will be my future brand of choice, as they got a lot of Hitachi HD tech when WD bought them and had to give it up. Toshiba’s been making drives for eons, and I believe the new stuff will be quite good. However for a NAS, I’d suggest their N300 line.

I and I’m sure most, would suggest you avoid a Z1 array unless you’re willing to loose the data should the unfortunate happen.

@mouseskowitz You can use partitions and such with FreeNAS, however you have to preconfigure the drive layouts before installing into the FreeNAS machine. Means running FreeBSD/TrueOS to partition and set up the drives. It’s not officially supported by FreeNAS as by design it’s one drive, one purpose.

It’s honestly not worth it, considering that small capacity drives are reasonably priced these days. You’re better off burning sata connectors than running partitions/logicals imho.

Be careful about L2ARC on lower-memory systems. ZFS needs memory to keep track of the L2ARC (about 400 bytes/block) and that can actually lead to memory starvation. See recommendations in
For instance, if you’re using a 120GB L2ARC with 4k blocks, that’s 3 million blocks total, and 12GB of memory usage just to support the L2ARC. That would likely drive a server with 16GB of RAM into an out-of-memory death spiral.