[OpenIndiana-discuss] Support for USB3?

[Jim Klimov]

6 ноября 2015 г. 0:59:52 CET, Ian Collins <ian at ianshome.com> пишет:
>Rich Teer wrote:
>> On Thu, 5 Nov 2015, Jonathan Adams wrote:
>>
>>> USB is good for ZFS on Linux (useful to set the ashift on a
>backwards
>>> compatible Solaris 10 zpool), but it's not really "prime time".
>> Just so that I'm absolutely clear, would I be correct in thinking
>that
>> eSATA is preferred over USB-3, assuming SAS isn't an option?
>
>eSATA works with Illumos, USB3 isn't supported.

(Disclaimer: Maybe it is FUD that follows, but one I believe ATM)

Also, over its long history, USB was not well known for reliability. Everybody cut corners here and there - cables, plugs, shielding (or lack thereof), controllers, firmwares, drivers. Even given the spec, somebody did not invest in implementing say 1% of corner cases, somebody else missed another % and overall the big stack is spotty - with different misses and errors depending on components you take and mix. Overall - who cares if a consumerish mouse or webcam has a hiccup? Reinit the session and try again.

On the other hand, storage technologies are more demanding in reliability and speed. There are also consumerish examples of corners cut, but at least you know one can always build an enterprisish stack of hardware pieces that works up to spec, though maybe not with sand-cheapest bits on the market. 

I gather (maybe wrongly, but it is a venue to research or discuss) that a SAS controller with external ports can drive an external SATA disk tower as well, and would cost some 100-200 bucks (depending on port count, vendor, model) for an IT-mode oem lsi hba card widely known to work well.

Anyhow, I've heard of enterprise storage components. I have yet to hear of enterprise USB ;)

A few years somebody wrote on the list that relying on USB as a permanent connection to a disk array is an open invitation for accidents to happen. It may be okay for plug-and-disconnect backups to removable media, but not quite good for life-long connections where you expect reliability. (That said, my home router with TomatoUSB "firmware" OS has an USB HDD plugged in so we have a shared storage cache for unimportant stuff at home - but it does often get lost from online access, and we have to shake the cabling or reboot the box to get the disk available again). 
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