[CentOS] LVM, usb drives, Active Directory

William Warren hescominsoon at emmanuelcomputerconsulting.com
Wed Dec 16 14:50:08 UTC 2009


On 12/16/2009 9:34 AM, Chan Chung Hang Christopher wrote:
> Steve Thompson wrote:
>    
>> On Wed, 16 Dec 2009, Chan Chung Hang Christopher wrote:
>>
>>      
>>> Steve Thompson wrote:
>>>        
>>>> On Tue, 15 Dec 2009, Scott Ehrlich wrote:
>>>>
>>>>          
>>>>> I have a client with a handful of USB drives connected to a CentOS
>>>>> box.   I am charged with binding the USB drives together into a single
>>>>> LVM for a cheap storage data pool (10 x 1 TB usb drives = 10 TB cheap
>>>>> storage in a single mount point).
>>>>>            
>>>> I tried doing this for fun once upon a time, using 6 1TB drives. I can
>>>> save you a lot of grief by suggesting that you don't think about this any
>>>> further. Boy is it slow. And extremely unreliable. And slow. Don't even do
>>>> it for backups. Did I say it was slow?
>>>>          
>>> Please qualify 'slow'. Was it dog slow, turtle-slow, snail-slow or
>>> slowaris slow?
>>>        
>> Slower than all of those. Top write speed I could ever achieve with a
>> USB-2 interface and SATA drives was 20 MB/sec with a trailing wind, and
>> usually half of that, with a single stream. I even tried USB-1 for more
>> laughs; 1 MB/sec on a truly good day. With multiple writers, performance
>> dropped so far as to be unusable (below 1 MB/sec). And we're talking mkfs
>> times in _days_. The host was a CentOS 5.2 box, 32-bit.
>>      
> Kudos to Steve for proving that USB2's 480mbits/sec is really just a sham.
>
> Now I wonder if you can daisy chain IEEE1394 devices...or try out
> eSATA...:-P
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>    
Any host based technology won't get you half of the claimed speed with 
any kind of reliability.  I don't think ti will ever really outrun 
something like SATAII or SAS.  What makes it funnier is Intel is saying 
this will make external RAID on USB possible...just keep in mind FRIAD 
and that's what USB RAID really is.


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