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

John Kerr johneddie.kerr at gmail.com
Tue Dec 10 13:43:07 EST 2013


Hi John

are your Raspi's 512 ram or 256?

John


On Tue, Dec 10, 2013 at 1:23 PM, John Van Ostrand <john at vanostrand.com>wrote:

> Be aware that Raspi is failrly slow at CPU and with external connectivity.
> I expect it may be fine for DLNA but if you have to move a lot of data to
> it often you may find the 100MB/s Ethernet is too slow.
>
> I have three RasPis running here at home and I have to remember the power
> savings I'm getting because they are slow compared to the speed of a
> full-blown server.
>
> That said, I'm all for the idea of putting low-end services onto a Raspi.
> Currently I'm happy with Asterisk running on it. I have a web server on
> another. Drupal page loads are about 3 seconds. My Perl-based wiki is much
> slower. But since they hardly see any hits I'm happy with slow performance.
>
> I tried a disk-server on Raspi, in fact it's still in place but I'm not
> using it. The real problem with disk and Raspi is that USB2 is too slow for
> the disk but the real bottleneck is the 100MB/s Ethernet. I'm more in
> favour of using a WDC MyBook NAS which supports NFS and costs about the
> same as a USB disk. You're not running Apache on it without hacking it
> first though and I don't know of any rooting options.
>
> There are other hardware solutions that are low power but have higher-end
> connections or other faster features. These are much more expensive and
> don't have the community that Raspi does. So I stuck with Raspi.
>
> I keep a spare Raspi and spare power bricks for hardware failure. It's
> still cheaper than a server and I can handle a little down time in case of
> failure.
>
>
> On Tue, Dec 10, 2013 at 5:07 AM, unsolicited <unsolicited at swiz.ca> wrote:
>
>> Good info, but meant CPU (horse)power, not electrical power. (-:
>>
>> - was expecting GHz not mA. (-:
>>
>> On that electrical power ... less need for usb hub power if external usb
>> (enclosures) are powered?
>>
>>
>> On 13-12-10 02:25 AM, Bob Jonkman wrote:
>>
>>> 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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>
>
>
> --
> John Van Ostrand
> At large on sabbatical
>
>
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