[kwlug-disc] How much CPU to keep a disk fed? [Was: Re: Which vendor for Raspberry Pi kits?]

Bob Jonkman bjonkman at sobac.com
Tue Dec 10 02:25:29 EST 2013


unsolicited wrote:
> Just how much CPU power does it take to keep a (USB? eSata?) disk fed,
> anyways?

A USB socket is required to provide 500mA. If you plug a USB extender
into computer, that computer's USB port can only supply 500mA for all
the ports on the extender (and the extender itself). That's fine for a
thumbdrive or two, but if you're trying to use an external, spinning
disk you'll need an extender with a power supply.  I've got a couple of
5+ year old external USB drives for which the cables have double USB A
connector, one for data+500 mA and the other for another 500 mA.

Don't know about eSATA, but on my computer the USB 3.0 port and the
eSATA port share one physical connector (ie. I can use either USB or
eSATA, but not both at the same time). So I suspect eSATA has the same
500 mA limit. OTOH, my external eSATA drive has its own power supply.

I was reading earlier this week that the new USB spec will supply up to
5A at 12V, which seems ridiculously high.
http://www.zdnet.com/new-usb-plug-coming-good-news-bad-news-7000023935/

--Bob.



On 13-12-09 11:17 PM, unsolicited wrote:
> Just how much CPU power does it take to keep a (USB? eSata?) disk fed,
> anyways?
> 
> (Guess it depends if you're running something checksumming, like BTRFS,
> I suppose, too?)
> 
> I've seen some mirroring (striping?) external USB boxes, but I wonder if
> catching a multi-GB rsync feed nightly would be beyond a Pi.
> 
> Note: My question, not Khalid's. Different beastie.
> 
> Are there other 'Pi' beasties out there?
> 
> 
> On 13-12-09 10:22 PM, Khalid Baheyeldin wrote:
>> I am considering building a small server that would have a largish USB
>> disk. The server would be rsynced from the main server, and runs minidlna
>> for access to photos, videos, music, ...etc.
>>
>> The Raspberry Pi seems like a good platform for this, being low power and
>> runs Linux.
>>
>> Online sites are selling kits that include a power supply, SD card
>> preloaded with NOOBS, and a case as well.
>>
>> So, the question is, anyone here order Raspberry Pis? Where did you order
>> it from? Canadian or USA based? Did they ship on time? Did you pay
>> customs?
>>
>> Looking for experiences, sites to avoid/recommend, ...etc.
>>
>> Examples I saw are Amazon, and this
>> http://canada.newark.com/raspberry-pi-accessories
>>
>>
>>
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> 
> 
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