Hi,

 

Does unraid support an external drive enclosure such as Silverstone SST-TS431U which connects to a PC via eSATA port multiplier?

 

Will unraid see all 4 drives and be able to create an array?

 

Thanks

unRAID's kernel configuration supports PMP capability on some controllers.

 

 

Silicon Image and Marvel come to mind.

Thanks.. is there a list of cards/chipsets with this support?

Thanks.. is there a list of cards/chipsets with this support?

 

There's no definitive list.

Controllers come and retire.

The silicon image chipsets support it as well as some marvels. You can scan the board for it.

It's mostly in the kernel.

The silicon image driver was one of the first that supported it. Marvell later. I'm not sure on the intel driver.

I've had the smoothest performance with Silicon chipsets albeit at a slightly slower performance.

There will be substantial performance limitation using more than 2 drives on eSATA due to the 3Gbps speed limit.

There will be substantial performance limitation using more than 2 drives SIMULTANEOUSLY on eSATA due to the 3Gbps speed limit.

 

For a single drive, it works fine, when accessing more then one drive, performance starts to dive.

 

I've tested many controllers with PMP. I've found the silicon image chipsets to be the smoothest.

I'm assuming this is because of the driver or command vs fis based PMP.

 

I.E. When using a silicon image chipset and accessing multiple drives, your speed is divided evenly among each drive.

 

Two access yeild 150MB/s each

Three 100MB/s

Four 75MB/s

 

This is a BEST case scenario.

 

Reality during my tests were,  Max speed 1 drive at 120MB/s,  2 approx 90, 3 Approx 60, 4 approx 30.

 

This means, during a parity operation requiring all drives, Check/sync/generate. if drives are read successively through the PMP port, the parity speed will drop.

 

I've never tested doing a round robin.

I.E. configure the array so that drives are interleaved per controller/PMP port.

 

Doing so may provide the benefit of full speed access to one drive at a time.

 

Now regarding my comment with 'smoothness'  With the Marvel and ASmedia controllers I found simultaneous drive access to be blocky.. I.E.  When access one drive at a high rate and adding another acceess, each process would read the drives in chunks or big blocks, thus cutting into how fast the whole operation would function.

 

With the ASmedia and 4 drive access, throughput dropped to 10MB/s.

Single drive access was at top speed, but once you accessed 2 drives at the same time. Each operation suffered.

 

This may be different with today's drivers. It's been a while since I've revisited this issue.

Thanks for the detailed information.

 

Apart from the initial configuration and parity check/sync, would a disk write typically require reading all of the drives to calculate the new parity information?

 

My intended use is as a media server, with writes to a single disk at a time - would this avoid the performance hit you describe?

 

Thanks for the detailed information.

 

Apart from the initial configuration and parity check/sync, would a disk write typically require reading all of the drives to calculate the new parity information?

 

My intended use is as a media server, with writes to a single disk at a time - would this avoid the performance hit you describe?

That would work but most of us do a parity check once a month and those will access every disk simultaneously and would be very slow.  It would be recommended that you also do a parity check once a month.

I tested with AMD Brazos

http://www.msi.com/product/mb/E350IAE45.html

 

And with this

http://www.aliexpress.com/item/Free-shipping-multi-SATA-1-to-5-Port-SATAII-SATA2-Multiplier-adapter-riser-card/715884490.html

 

Working without problem with Unraid 5.x

 

Thanks.. is there a list of cards/chipsets with this support?

List of supported Chipsets:

https://ata.wiki.kernel.org/index.php/SATA_hardware_features