Is it ok to use TrueNAS with SSDs? I keep seeing the Western Digital 4TB WD Red SA500 NAS being recommended. Why? It’s more expensive than the Crucial BX500 and the equivalent Western Digital Blue 4TB.
Price is only part of the issue with SSD’s
Longevity in all its forms is perhaps more important
Are you saying SSDs won’t last long?
Look at the TBW (Terrabytes written) numbers or DWPD (Drive writes per Day) to get an idea, of what the manufacturer claims and if this will be ok for your usecase.
Yes.
Not all SSDs are created equally.
There are different factors that define the worth/potential use case(s) of an SSD.
Here is a definitely incomplete list:
- capacity
- form factor (2,5", M.2, U.2, E.2, PCIe card…)
- warranty
- as @Farout said and among the most important: TBW (which together with the warranty time is used to calculate DWPD and tells you how much data can be written to the SSD)
- interface (SATA, SAS, NVMe…) which most importantly but not only limits the maximum performance and brings us to
- performance (sequential speeds, IOPS…)
dont forget about the different types of flash storage qlc tlc mlc which can also have an impact on sustained writes
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of course, we haven’t even touched DRAM cache vs HMB vs no cache at all yet.
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How many drives do you plan to use and in what configurations?
Pending on workload, the cheaper BX series (no DRAM cache.) may perform fine since TrueNAS has ZFS to use RAM for cache, which is faster…
SSD’s can last for years, or die the next day, same as spinning rust drives…
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I hace a RAIDZ1 volume made up of 5 2TB Patriot SSD’s with 1 hot spare. My volume is used for access to documents through a WebDAV server, SMB shares and video recorded from a Frigate NVR. This volume has been in use for a year now and I haven’t had any issues with any of the SSD’s.
That sounds like a very very overkill setup for the use case to me 
But hey, better this way than the other way around.
I’d just be careful with NVR and consumer SSDs.
Have you taken a look at the SMART values recently - I’d find it interesting to see the amount of data written after about one year of NVR usage, possibly with some write amplification.
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What is a hot spare? How is it used?
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A hot spare is an unused disk already present in the system that can automatically replace a failed disk.
A cold spare would be an unused disk sitting on a shelf, ready to be put into the system if a disk fails.
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I don’t want to open this can of worms here…, but as I understand it (which admittedly changes every few months… ),
a single hot spare for just one RAIDZ1 vdev doesn’t seem as beneficial as simply including that drive and building a RAIDZ2 instead.
Sure, with an SSD you don’t have the same issue as with HDDs, where the spare is spinning all the time and still accumulating wear even while “idle.”
And yes, a hot spare can be detached and re-purposed elsewhere if needed, which is a nice bit of flexibility.
But apart from that, I mostly see RAIDZ2 as the better choice, in this scenario
- higher built-in redundancy (2-disk fault tolerance, even during resilver)
- all drives age evenly, no single “antique spare” sitting idle for years
- usable capacity is nearly the same
- performance difference is minimal on SSDs
Am I missing something else here?
Is there a case where a hot spare would really be superior in a single-vdev SSD setup?
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Hot spares are shared, so for a pool with several vdevs, one or a few hot spares may make sense over going globally for the next redundancy level.
Otherwise you’re correct that raidz2 is better than raidz1+spare, or that raidz3 is better than raidz2+spare.
Then there’s no raidz4, so raidz3+spare may make sense for a remote backup system where timely maintenance is not practical. But that’s more of a use case for HDDs.
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Is there a case where a hot spare would really be superior in a single-vdev SSD setup?
Well, hot spares are not written to, so their TBWs won’t be wasted until their activation…
Tangential question: do hot spare HDD spin at all or are they kept spun down?
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With the default settings nothing is going to spin down.
Some things can change this, the power settings in TrueNAS for example.
There are also drives that automatically spin down due to how their firmware is set up. This can lead to constant spindown/spinup events, which ends up causing wear and tear.
Why’s it overkill? I’ve also mentioned that the volume is used for Documents which I’m very concerned are reliably stored and available. They take up the bulk of the Volume whereas the NVR usage is minimal
I meant overkill in terms of performance, not reliability.
Ok. I was also interested in minimizing power consumption.