Experiences using USB HDD's in array?

[_jonte]

Hi,

Any experience using USB HDD drives in your arrays?

Problems, limitations, generally bad idea, excellent idea, etc..?

 

My mini-ITX board only has four SATA ports, used by three SSD's and one 2TB HDD. Plus one 2TB USB HDD connected as an unassigned device for media storage. 

So my "array" consist of one old 2TB HDD and no parity drive... (yeah, got backups)

No free PCI-slot.

 

Stuck with two options?

1: Remove the oldest SSD (60GB) for an extra HDD. Still limited to only two drives though. 

2: Get another 2TB USB HDD and use both for array, with the 2TB SATA as parity.

 

What would you do?

 

[mr-hexen]

USB drives cannot be used as an array disk.

[trurl]

35 minutes ago, mr-hexen said:

USB drives cannot be used as an array disk.

Actually, USB drives in array or cache has been supported since 6.2b18

I don't think a lot of people have tried it though.

[Vr2Io]

Sure it is not a good idea, curently I have an unRAID run on QNAP HW, it haven't PCIe for add-on.

Due to I want utilize it, so I add a cheap 5 bay USB enclosure (less then USD 100). In first, it have many problem, always reset/disconnect ( even test on a Windows PC ), can't read SMART etc ...

Finally, test/try and search on Internet almost 2 months, I got a solution by changing (1) Encloseure firmware, (2) Add a VIA USB hub between them, then it work stable.

 

BTW, it still have limitation,

(1) Don't let unRAID spin-down the HDD in enclosure, the disks will spin-up after few secord, and may cause the enclosure reset.

(2) Total BW will be ~300MB/s, that means if connect with 5 HDD, parity or disk check will got 60MB/s for all array disks.

(3) Disk Identification not be usual, i.e. last 3 disk in enclosure. So change disk or slot location, you need remove/add them again in array.

 

Anyway, this is my case, different HW will got different result.

 

Edited March 28, 2017 by Benson

[_jonte]

Thanks @Benson!

Sounds like you have been pretty unfortunate. Do you think much of your problems are caused by "cheap" hdd-enclosures? Or do you think they are more software related?

Have you tried using any of the drives as an unassigned device, and did you experience the same issues then?

I'm asking because my USB-drive works perfect as unassigned ntfs drive. Smart works e.g., and I have not had any issues when the drive identification has changed.

I will have to check whether the disk spins down properly or not. 

Disk speed are not very critical for me, but 60MB/s total sounds very slow! Perhaps because you use an USB hub?

[_jonte]

15 hours ago, trurl said:

Actually, USB drives in array or cache has been supported since 6.2b18

I don't think a lot of people have tried it though.

Yeah, haven't found anything searching the forums. 

Any thoughts to whether it's decent solution, or generally a bad setup?

[JorgeB]

I did some limited testing, it worked, but more than one disk on the same USB controller was noticeably slow, so if your board has a two USB 3.0 controllers you should be OK with 2 disks, if they share the same controller you'll probably notice slowdowns during parity check/disk rebuilds.

Edited March 28, 2017 by johnnie.black

[_jonte]

24 minutes ago, johnnie.black said:

I did some limited testing, it worked, but more than one disk on the same USB controller was noticeably slow, so if your board has a two USB 3.0 controllers you should be OK with 2 disks, if they share the same controller you'll probably notice slowdowns during parity check/disk rebuilds.

There is only one USB entry listed under PCI-devices, so only one USB controller then?

However the USB 3.1 is 5 Gbps, while SATA is 6 Gbps. I'm thinking 2.5Gbps (~300MB/s) per drive would be good enough? 

Do you have full 5Gbps "Superspeed" on your USB controller?

 

Edited March 28, 2017 by _jonte

[JorgeB]

1 minute ago, _jonte said:

USB 3.1 is 5 Gbps

 

Yes, but at least in my tests it didn't handle concurrent access well (I tested on USB 3.0), much slower than half the speed with a single device.

 

Also max theoretical bandwidth and real world speeds are always different, but for me with USB 3.0 they were much different, in my tests with a single SSD speed was anywhere from 150MB/s to 250MB/s max depending on the USB controller and the SATA-to-USB adapter used.

[_jonte]

2 minutes ago, johnnie.black said:

 

Yes, but at least in my tests it didn't handle concurrent access well (I tested on USB 3.0), much slower than half the speed with a single device.

 

Also max theoretical bandwidth and real world speeds are always different, but for me with USB 3.0 they were much different, in my tests with a single SSD speed was anywhere from 150MB/s to 250MB/s max depending on the USB controller and the SATA-to-USB adapter used.

Thats true.. I will have to do some research on that. Perhaps USB 3.1 handles it better.

Did you notice any functionality/features missing compared to SATA disks?

[JorgeB]

Like Benson mentioned disk identification changed, so if you swapped that disk to a SATA port unRAD would complain that the disk is wrong.

Edited March 28, 2017 by johnnie.black

[_jonte]

Just now, johnnie.black said:

Like Benson mentioned disk identification changed, so if you swapped that disk to a SATA port unRAD would complain that the disk is wrong.

Thanks for you help!

[Vr2Io]

If your USB-drive works perfect as unassigned ntfs drive ( in fact no matter what FS is ), I'm sure this won't got problem be an array member.

During 2 months troubleshoot, I found most 2+ bays enclosure also got same problem, always crash / reset, the issue relate to thier chipset solution - Jmicron.

There are hard to found other chipset solution for 2+ bays enclosure.

The hub haven't slow down the speed, it is 1-to-1, if without it the enclosure will reset all time during mass read/write.

Edited March 28, 2017 by Benson