[kwlug-disc] Multi-bay docks ... 1 at a time??? [Was: Re: Linux-compatible eSATA expansion cards]

Tue Aug 5 18:12:34 EDT 2014

Somewhere in the thread someone mentioned "This depends on your chipset.".

All data transfers whether IDE, SATA & USB are channeled through the 
same choke points in the chipset.
(as mentioned Southbridge)

Chipset support through the various Linux OSes could be variable.

A h/w designer/vendor I know was using a MARVEL WIFI chip on an embedded 
Linux platform.
A floss driver for the chip did not produce the expected throughput.
He had to rewrite the driver.

I know this may not be the same with cpu / northbridge / southbridge 
chipsets and the Linux OSes as a whole becuase there should be vetting 
and QA in the process.

JohnJ

On 2014-08-05 13:32, unsolicited wrote:
> What caught your eye in the links that bears on the conversation at hand?
>
> On 14-08-05 12:56 PM, John Johnson wrote:
>> I have no opinion or experience to share but thought that the following
>> links might be helpful.
>>
>> Ref: http://en.wikipedia.org/wiki/Chipset
>> Ref: http://en.wikipedia.org/wiki/Northbridge_%28computing%29
>> Ref: http://en.wikipedia.org/wiki/Southbridge_%28computing%29
>>
>> Note: According to one of the above, IDE, SATA & USB are on the
>> Southbridge chip.
>>
>> JohnJ
>>
>> On 2014-08-05 12:07, unsolicited wrote:
>>> On 14-06-30 09:53 PM, Khalid Baheyeldin wrote:
>>>> On Mon, Jun 30, 2014 at 8:09 PM, Paul Nijjar <paul_nijjar at yahoo.ca>
>>>> wrote:
>>>>
>>>>> In an ordinary situation, maybe. However, in this computer I am
>>>>> planning to use all the internal SATA connections for other drives.
>>>>>
>>>>> Honestly the differences between eSATA and SATA still confuse me, 
>>>>> even
>>>>> after reading the Wikipedia article. Is it true that not all SATA
>>>>> ports on a motherboard can be converted to eSATA with these
>>>>> connectors?
>>>>
>>>> One important difference is hotpluggability.
>>>> This depends on your chipset. There is a table here listing the
>>>> supported
>>>> chipsets.
>>>>
>>>> https://ata.wiki.kernel.org/index.php/SATA_hardware_features
>>>>
>>>> That page also lists PMP, if you want to attach more than one device
>>>> to the
>>>> same eSATA cable. Although, when I tried it with a dock that has 2
>>>> drives,
>>>> one drive would have normal speed and the other would be really
>>>> slow.  ...
>>>
>>> Summary: Am I understanding the availability of possible solutions to
>>> moving vms between computers (especially future laptops - single esata
>>> port / USB 3 availability / no PMP controller) correctly?
>>>
>>>
>>> Happened to poke and google around the web on this over the weekend.
>>> Playing with vbox and wanting to move vms around my internal net -
>>> leading to the need for GBs of extra space on both source and
>>> destination. Over my net, ~35GB vm takes just over an hour to copy,
>>> slow machines. Fast machine on one end about 1/2 hr. Same for machine
>>> to external drive on USB 2 (to and from -> 1 hour). So happened to
>>> poke about docks / what they and storage might cost. Idea of USB 3 /
>>> SSD is attractive, but seems cost prohibitive. Also leads to the idea
>>> of running the vm off external device, and schlepping to different
>>> computers as needed. e.g. Hardware failure. Even if I don't have USB 3
>>> & eSata on every machine today, presumably each new machine will at
>>> least have USB 3.
>>>
>>> Given Khalid's note above that points out that dual-bay docks are
>>> essentially pointless (more than 1 drive, slow on other drives), I
>>> wondered why / what's up. Seems like whatever (multi-bay) such is
>>> plugged in to must be -TO- a port multiplying sata controller or this
>>> slow drive problem is run in to. Since PMP isn't required for a sata
>>> controller, most everyone will be out of luck unless they know to
>>> specifically search for such capability beforehand. (Making it seem
>>> like multi-bay docks are are marketing ploy - most things you might
>>> connect to can never take advantage of it?)
>>>
>>> Seems that only 1 drive can be talked to at a time (Command Queuing?)
>>> / something PMP must be in the sequence to do the 'multiplexing'(since
>>> any one drive can't saturate a SATA link unless it's an SSD) to try to
>>> keep the link to the computer going full bore.
>>>
>>> Yet it does not seem that PMP is available at the device
>>> (dock/adapter/drive) end - it has to be in the controller, and I
>>> expect its unlikely for laptops to have them. Does this not:
>>>
>>> - render multi-bay docks pointless (unless a 'duplicator' or RAID)?
>>>
>>> - make simple adapters attractive e.g.
>>> http://www.canadacomputers.com/product_info.php?cPath=95_96&item_id=35385P 
>>>
>>> more sensible - except still have problem of providing power to drive
>>> if large capacity / 7200 RPM? (Let alone, not normally stocked?)
>>>
>>> - if eSata,
>>> http://www.amazon.ca/eSATA-External-Bridge-Adapter-Converter/dp/B00DHCC7NQ/ref=sr_1_2 
>>>
>>> or
>>> http://www.amazon.ca/Anker%C2%AE-Uspeed-Converter-Adapter-External/dp/B006J2L0ZM/ 
>>>
>>> ?
>>>
>>> - render eSata useless vis a vis USB 3. i.e. New laptops will not
>>> likely have multiple eSata ports - if any at all, but will likely have
>>> multiple USB 3 ports (yet USB can do the multiplexing itself so no
>>> need for PMP?)
>>>
>>> - make NAS / RAID-JBOD units make more sense as it will be managing
>>> the (single) link to computer flow? Yet the point of adapters/docks is
>>> quick disk flipping about, rather than digging into a (NAS) enclosure!
>>>
>>> - unless a laptop, live with digging into the case when moving drives
>>> around. Back to advantage of cages, e.g.
>>> http://www.icydock.com/goods.php?id=175
>>>
>>> So, it seems a single bay dock is the only thing that makes any sense,
>>> and if multiple drives are needed, purchase multiple single bay docks.
>>>
>>> Yet I see 3TB limitations on drive sizes for such, and 6TB drives are
>>> now here, with 8TB drives soon to come. I do see that
>>> http://www.canadacomputers.com/product_info.php?cPath=14_679&item_id=047936 
>>>
>>> notes 'Up to 6.0 TB*', but it is not clear that that does not mean
>>> MAX. 3TB PER BAY!
>>>
>>> I'm guessing this has more to do with the USB chipset in use only able
>>> to understand MBR drives, not GPT.
>>>
>>> Seems like a net. NAS makes more and more sense, but schlepping GB of
>>> images over the 2Gbps network vs local 6GBps sata III seems
>>> counter-intuitive.
>>>
>>> Am I understanding the availability of possible solutions to moving
>>> vms between computers (especially future laptops - single esata port /
>>> USB 3 availability / no PMP controller) correctly?
>>>
>>>
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>>
>>
>>
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