Even though I built my server under a year ago, I can see a time in the near future where I will run out of storage space.  

 

At the moment I have 1 free HDD connection so my plan is to upgrade my Parity to 8TB+ and move my current 6TB parity to the array.  My next upgrade would then be to remove my 2 small 250GB cache drives, add 1 500GB SSD to the remaining one and use the connection freed up to buy another 8TB+ drive to my array.

 

After that, I want to avoid selling smaller drives as most of my drives are already 5TB+ so I won't get a massive increase.  

 

It looks like my best option will be get an External USB Drive enclosure and chuck in 2 or more HDDs.  These are relatively cheap https://www.amazon.co.uk/StarTech-inch-Dual-Drive-Enclosure/dp/B00M77UOC8 compared to my other options which I think are:

 

(i) replace my mobo for one with more PCI-e slots so I can buy a SATA card, which will probably also mean I need to buy a bigger case - $$$$$$$

(ii) build another cheap unRAID box just to do storage overflow (no dockers, VM so can go very basic spec) - would be connected via ethernet as no space on my current unRAID box to add a 10G card - $$$$

(iii) build a dedicated pfsense box to free up a PCIe slot to add a storage card to add 2 more drives

 

My questions are, does anyone have experience of using USB drives and/or external enclosures?  Is the performance adequate for playing media files - blu-rays etc? Can anyone recommend a cheap dual enclosure or dock?

 

Thanks in advance

I've seen posts regarding problems assigning USB hard drives into the array, but I haven't tried it myself so I'll only say - get advice on how well that will work.

 

That said, you'd max out the bandwidth of USB 3.0 with only a few hard drives during heavy concurrent operations like parity checking.  5 gb/s = 640 MB/s, and bandwidth tests I've seen of USB 3.0 have maxed out around 300 MB/s.  I think you should look at solutions where your hard drives are attached via PCIex controllers.

17 minutes ago, tdallen said:

I've seen posts regarding problems assigning USB hard drives into the array, but I haven't tried it myself so I'll only say - get advice on how well that will work.

 

That said, you'd max out the bandwidth of USB 3.0 with only a few hard drives during heavy concurrent operations like parity checking.  5 gb/s = 640 MB/s, and bandwidth tests I've seen of USB 3.0 have maxed out around 300 MB/s.  I think you should look at solutions where your hard drives are attached via PCIex controllers.

Good points.  I just checked though and my Toshiba X300s get around 150MB/s http://hdd.userbenchmark.com/Toshiba-X300-6TB/Rating/3594 so if I chucked two of them in an external enclosure assuming there aren't any clashes, it shouldn't slow my overall array down too much.

9 minutes ago, DZMM said:

it shouldn't slow my overall array down too much.

 

It shouldn't slow too much, though it will some, but more importantly, USB error handling is much worse than SATA, mainly for that I wouldn't use USB disks in the array.

41 minutes ago, johnnie.black said:

 

It shouldn't slow too much, though it will some, but more importantly, USB error handling is much worse than SATA, mainly for that I wouldn't use USB disks in the array.

Thanks.  I think I'll investigate building a pfsense box to free up a x4 slot so I can add more drives including esata.  I'm sure I can do this for less then the 300+ pounds it'll cost to update my mobile and case.