[Arm-netbook] A10 server dreamboard

[Gordan Bobic]

On 05/29/2012 04:06 PM, Enrico wrote:
> On Tue, May 29, 2012 at 4:52 PM, Gordan Bobic<gordan at bobich.net>  wrote:
>> On 05/29/2012 03:40 PM, Tsvetan Usunov, OLIMEX LTD wrote:
>>>>> - as much as possible ram
>>>>> - 512 MB flash (not more, if you need more space you have sata)
>>>>
>>>> Why not do away with flash completely and put a uSD slot on instead of
>>>> the flash?
>>>
>>> SD-card have mechanical movable parts, it'r reliability may decrease with
>>> time due to moisture, dust etc. having 4GB NAND flash on board will be much
>>> more reliable than SD card on socket
>>
>> That's debatable. The chances are that those that want to use it will
>> plug in an uSD card and leave it there. In that state I wouldn't imagine
>> reliability would be negatively impacted. I've never actually seen a uSD
>> slot fail, and I have had a lot of devices with such slots for a number
>> of years.
>>
>> Plus if you do use it heavily, flash wears out - at least uSD card is
>> replaceable.
>
> A nand flash easily outperforms a good uSD, especially on random
> access.

Random reads aren't a problem. Random writes on most flash that isn't 
proper SSD grade sucks:

http://www.altechnative.net/2012/01/25/flash-module-benchmark-collection-sd-cards-cf-cards-usb-sticks/

UBIFS or similar may glaze over it on NAND by linearizing writes in it's 
wear leveling - I haven't tried so cannot comment.

> It will have only the rootfs so wearing will not be a problem.

You'd be surprised. Just booting up typically causes 5-10MB to be 
written out to disk. Check vmstat -d after booting and after a bit of usage.

>>>> If you are going for density, then you might as well go to the logical
>>>> conclusion with EOMA "blades" and cram 40 or so into 1U. And that will
>>>> still leave you plenty of space for an internal ethernet switch,
>>>> internal serial switch (for console access), some 2.5" SATA bays (maybe
>>>> with a "NAS node"), maybe even an internal UPS.
>>>
>>> but how then the USB will be bring on from of the rack in this case?
>>> extension cables?
>>
>> Not at all. You don't need USB to come out of the chassis. You
>> ssh/telnet to the serial console switch, (a-la Lantronix) and from there
>> connect to whichever node's console you want.
>
> While i think that maybe you don't need to have all the usb come out
> of the chassis, maybe some sort of predisposition for some (2?)
> extension cables could be useful. This is something to think more
> about it.

You haven't made a case for why you'd actually need USB when you have 
serial console accessible via ssh.

Gordan