What are your thoughts in using a WD Purple SD card to hold the filesystem in a Rockstor home NAS?
I already have an HPE ProLiant MicroServer Gen10 Plus V2, and purchased 4x HP Converter 2.5" to 3.5" SAS/SATA Adapters so that instead of 3.5" spinning drives I want to use 2.5" SSD drives that will be 4x WD Red SA500 4TB in RAID10 with btrfs through Rockstor.
The server has an internal vertical USB drive port soldered to the mobo I can connect a 5th drive. I don’t wish to use regular flash drives since those don’t include wear levelling, so I thought of either using a WD Purple SD card with a SanDisk MobileMate adapter, or SanDisk Extreme PRO drive.
@jpff welcome to the Rockstor community. I think USB flash drives actually do contain wear leveling, so if you overprovision it sufficiently (I.e the bigger, the better) you won’t have wear related problems (same overprovision recommendation would go for an SD card, too).
Just to clarify when you meant “file system” above you meant the installation of the Rockstor appliance, not as a data storage component for your RAIDs?
I am not sure that the U1 class of the SD card is sufficiently fast (it’s like 10MB/s right?) for what your box can do/handle.
Just an opinion, but I would get at good USB3.0 /3.1 (depending on what the server can handle) flash drive with e.g 500GB and use that.
But in the end, if the performance of the SD card works well enough for your workload, it might just work out. But we have seen with older USB stick setups when they were too slow on an Intel architecture box, the OS would really struggle to even get off the ground (both old CentOS as well OpenSUSE that’s now the underpinning of Rockstor).
There exists another popular NAS OS solely running the OS from USB-Sticks (hint: UNRAID). So first, there are a lot of successfull deployments of home-NAS systems running the root FS of a USB-Stick and secondly, when you take a look at their forum, you find a lot of recommendations regarding “the correct” USB-Sticks.
And also to my knowledge, SD-Cards and USB-Stick use basically the same (consumer grade) Flash in another formfaktor, with the main advantage of SD-Cards that they fit inside other devices (e.g. Camera) instead of dangling on the outside (USB-Stick).
Furthermore, as @Hooverdan already pointed out is the transfer speed of the SD-Card you mentioned (Class 10 / UHS1 = 10MB/s) not the fasted.
If you want an “easye” setup I would also recommend a “good” USB 3.0 (or higher) Stick. I don’t see any benefit in using an SD-Card over a USB-Stick.
In general, the fewer parts and less connectors, the better and more reliable (i.e. the USB to SD-Card adaptor is another part that could fail and in general is not meant to be used 24/7).
On the other hand, if you wan’t “server grade” and potentially more endurable storage, get an external USB-SSD (and mount it internally in the server with zip-ties, if you find space) or an USB to M.2 adapter and insert a siutable M.2 SSD.
(Hint: be aware that for M.2 there are differen keys (B/E) and protocols (SATA / PCIE) and that your adapter fits you SSD)
From what I’ve read there’s a huge range in the quality of USB sticks and that’s not surprising considering the equally huge range in prices.
At the low cost level it’s the complete wild west. Apparently people have opened cheap, no-name USB sticks and just found repurposed SD cards or other clearly pre-used flash chips soldered in there. Or so I’ve read. You shouldn’t expect much from this market segment – to include wear levelling.
Then there’s the higher priced but still consumer grade market where you have the big name brands. From what I’ve found on various forums just now, you should generally expect that all modern USB sticks from the well known manufacturers include some sort of wear levelling chips, although even these manufacturers will just swap out components willy nilly for the same product and even sometimes in the same batches, so their support isn’t able to give any specifics on algorithms etc. when asked. I found a few forum posts where people actually wrote to various support addresses and got very unspecific answers back.
Still, that might be a way to go.
And then there’s the industrial end of the market where manufcaturers actually do give guarantees and specifics about their USB stick’s features, including wear levelling. They’re a bit hard to find and not cheap, though. (As an example, I found a Swissbit 64GB drive for over 100 €…)
Thus, if you want to use the internal USB port, I would also recommend using a good USB 3.x stick, either from a big name brand (and make sure it’s an original - bargains can be fakes!) or even one marketed as industrial.
As an alternative, if you don’t have an M.2 slot on your motherboard, but you do have a free PCIe port, you could consider using an M.2 adapter for PCIe and an NVME SSD. You’d have to make sure that the firmware can boot from that, but that should give you a pretty robust setup, I think.
I want to to thank everyone who gave their opinion on this.
I admit I’m a bit scared of flash drives when it comes to leaving them plugged 24/7. I had a Philips FM16FD05B (still laying on my desk for some reason) that I kept attached to my desktop 24/7 that held my keepass database fail / become corrupted. I never had an issue with SSDs though, not a failed one thus far.
Just to clarify when you meant “file system” above you meant the installation of the Rockstor appliance, not as a data storage component for your RAIDs?
Yes, I meant to hold the OS filesystem, my apologies for not being clear enough on that.
And indeed, now that you point that out, U1 may be too slow, and as simon-77 pointed out, having a SD card adapter that’s meant for temporary use, and not 24/7 use, is another point of failure.
As tachikoma mentioned, industrial grade would be desirable, but I feel SLC memory is far too expensive for me for this purpose..
As an alternative, if you don’t have an M.2 slot on your motherboard, but you do have a free PCIe port, you could consider using an M.2 adapter for PCIe and an NVME SSD.
This is fantastic! Honestly didn’t even consider this. I believe the server does have a PCIe slot, I believe it was meant for an extra NIC? But can be used for this purpose and I can use, for example, a WD Red SN700 1TB SSD M.2 there to hold the OS file system!