esata

[adler-wRvlPVLobi1/31tCrMuHxg at public.gmane.org (Stephen Adler)]

Something tells me that the port multiplexer will degrade the 
performance of your disk array. Is this of any real concern?

Jarod Wilson wrote:
> On Nov 19, 2009, at 11:01 AM, Stephen Adler wrote:
>
>   
>> I want to expand the disk capacity of a server which is stuffed with 
>> drives already. So now I'm thinking that I should consider an external 
>> device which holds several sata disks. This is my first exposure to 
>> external sata drives and I want to make sure I'm not doing something 
>> dumb. One thing which I've noticed is that the usual one drive per sata 
>> port does not seem to apply. The external boxen I've found on the net 
>> have a single esata port which drives multiple disks. So, if I buy one 
>> of these external drive enclosurs and install two drives, will linux see 
>> the two drives individually as /dev/sdc and /dev/sdd? Or will I only see 
>> one raided drive. These boxes seem to have raid built into them.
>>     
>
> A lot of them do NOT have RAID built-in, they actually rely on the controller they're hooked up to for RAID functionality. Many of these boxes come bundled with an eSATA controller for that very reason. A single sata port off your motherboard with an external bracket may not actually support port multiplexing, which is necessary for these multi-disk boxes.
>
>   
>> Since 
>> I'm currently using software raid on my linux setup, I want to have 
>> access to each individual drive so I can add them to my current raid array.
>>     
>
> Most of them that I've seen do off JBOD mode.
>
>