USB External Hard drives UNRAID system combined with SATA?

[miogpsrocks]

 

 

If I purchase a motherboard with 12-USB ports. Can I purchased 12 external hard drives and use unraid with the external hard drives? 
 

Is there a reason that USB port with external USB hard drives enclosures will not work? 

 

Please let me know

 

Thanks. 

Edited October 28, 2020 by miogpsrocks

[JonathanM]

There is a small chance that it might work sometimes, but the odds are good that it will not work well or at all.

 

Unraid requires constant reliable communication with all array devices that each have unique and unchanging device identification.

 

USB typically fails on multiple of those requirements. Even if you get almost all of those solved, USB protocol in general is bad about momentarily dropping and reestablishing connections, which will fail a drive out of the array.

[miogpsrocks]

1 hour ago, jonathanm said:

There is a small chance that it might work sometimes, but the odds are good that it will not work well or at all.

 

Unraid requires constant reliable communication with all array devices that each have unique and unchanging device identification.

 

USB typically fails on multiple of those requirements. Even if you get almost all of those solved, USB protocol in general is bad about momentarily dropping and reestablishing connections, which will fail a drive out of the array.

 

So long story short, USB external drives are good enough for desktop storage but not good enough for UNRAID(and probably RAID) setup due to micro disruptions in the connection? 

 

That is a shame. 

[trurl]

1 minute ago, miogpsrocks said:

due to micro disruptions in the connection

If that were the only problem you might get away with using them in an array that didn't use parity, since there would be nothing for them to be out-of-sync with.

 

But not having

1 hour ago, jonathanm said:

unique and unchanging device identification

is going to be a total non-starter.

[miogpsrocks]

1 hour ago, trurl said:

If that were the only problem you might get away with using them in an array that didn't use parity, since there would be nothing for them to be out-of-sync with.

 

But not having

is going to be a total non-starter.

 

When you say " unique and unchanging device identification", don't external hard drives have unique serial numbers? 

 

I run test of hard drive using software like seatools and crystal disk info and these hard drives have a lot of information that pulls up. 

 

The software can't link some kind of unique identifying information on a hard drive as a particular disk in the parity setup? 

 

For me, it would be easier to have a shelf filled with external hard drives then trying to piece together some kind of monster  system that can fit so many drives then have to tear the external hard drive apart to connect them inside the PC/Server. 

 

If you are using this Cache SSD, then it first writes to the cache drive then writes to the array. 

 

Understand its not going to be enterprise level performance but for the guy who need archival and available of data, this may be the best bang for the buck  but sadly is sound like this software does not support this kind of thing from what I am hearing. 

 

Thanks. 

[trurl]

2 minutes ago, miogpsrocks said:

this software does not support this kind of thing

It is allowed by the software, but not all possible hardware will work well, and all possible hardware in the case of USB external drives is very much a moving target, unlike standard SATA and SAS connections.

 

Many hardware implementations of USB external drives have exhibited one or more of these problems:

• Non-unique identifiers, so Unraid can't determine which disk is supposed to be assigned to which slot in the array.
• Presenting drives with a non-standard size. This won't matter if not using parity, but parity can't be smaller than any data disk, not even by one byte.
• Not passing SMART information, so drive health can't be monitored by Unraid.
• Disconnects which causes a disk to be out-of-sync with parity. When this happens the disk is "kicked out" and has to be rebuilt. This will take several hours, depending on size. And it may happen frequently. This is why I said it might be OK without parity. But of course, without parity, you can't recover a failed disk.

Probably others I am not recalling or not aware of.

 

Another thing that is asked about is trying to use an external enclosure with a single USB connection for multiple disks. Parity operations are intended to work in parallel and if they can't performance is significantly affected.

 

Much of this is unimportant for a single external drive that often isn't even connected all the time, which is the intended market for these designs.

 

 

 

[JonathanM]

9 minutes ago, miogpsrocks said:

When you say " unique and unchanging device identification", don't external hard drives have unique serial numbers? 

Yes. However, the enclosure may not pass that ID through properly, and many USB SATA adapters mangle the numbers or substitute their own ID instead of passing the drive's true ID. Also, some enclosures properly pass SMART info, some don't.

 

It depends on the enclosure. But, since USB is so bad about connection integrity, there isn't a body of knowledge on what works best, because even when it works the best it can, it's still slow and problematic compared to SATA or SAS.

 

So, it's possible to get something to work the way you are asking, but you will be dealing with trial and error, mostly error. Is the hassle factor worth it, when the final product is guaranteed to be slower and less reliable than the well established alternative?

 

16 minutes ago, miogpsrocks said:

For me, it would be easier to have a shelf filled with external hard drives

How would you cool them? External drives aren't engineered to be run continuously, they will overheat without some sort of forced airflow or other cooling.

 

All that being said, there is nothing stopping you from forging ahead and trying it. Unraid will definitely let you set it up exactly as you propose, as long as each drive sends a unique serial number that Unraid can use.