Re: [gentoo-user] Questions about SATA and hot plugging.

Dale <rdalek1967@×××××.com> [10-12-14 17:48]:
> Hi,
>
> I got one more hard drive to move over and it is SATA.  Question one,
> can the new mobo's do hot plugging for SATA drives?  I have a plug on
> the front of the case and was wondering since it is on the front if
> they can be hot swapped or if I need to shutdown then hook it up.  If I
> can hot swap, where does the power come from?  I know the drives I put
> in the case have a separate power connection.  How's that work exactly?
>  Is that just for external drives that have their own power?
>
> I have two dries in here already.  One I bought and one that was
> donated.  This is what hdparm reports:
>
> fireball ~ # hdparm -tT /dev/sda
>
> /dev/sda:
>  Timing cached reads:   6788 MB in  2.00 seconds = 3395.32 MB/sec
>  Timing buffered disk reads:  328 MB in  3.01 seconds = 109.06 MB/sec
> fireball ~ # hdparm -tT /dev/sdb
>
> /dev/sdb:
>  Timing cached reads:   6736 MB in  2.00 seconds = 3367.58 MB/sec
>  Timing buffered disk reads:  324 MB in  3.01 seconds = 107.69 MB/sec
> fireball ~ #
>
> Is that about normal?  The mobo is 3Gbs/sec and the drives are too.
> Shouldn't they be faster than that?  I read at one time that SATA is
> basically plug up and it works.  Just checking if there is a setting I
> need to change.
>
> Related to the above, in the BIOS, it is set to Native IDE.  Should
> that be set to AHCI instead?  Is that why it is slower than expected?
> Is that good to go with Linux as well?  I have this set in the kernel
> and built in as usual:
>
> AHCI SATA support
>
> Let me know if I am somewhat right on anything.  Oh, I decided to name
> the new rig fireball instead of lightening.  ;-)  You may notice that
> in the paste up above.
>
> Thanks.
>
> Dale
>
> :-)  :-)
>

Hi Dale,

as I know, the hd hardware can't nearly as fast as the bus speed
regardless whether it is 6GB/s or 3GB/s.
Quickly doing the same as you on my harddisk gave:

/dev/sda:
 Timing cached reads:   6726 MB in  2.00 seconds = 3364.06 MB/sec
 Timing buffered disk reads: 318 MB in  3.00 seconds = 105.93 MB/sec

The speeds of 6 GB/s or 3GB/s are only reached, when reading data
directly from the hd cache.

I dont know, what motherboard you use. But the settings you describe
seem to be identical to mine.

Important is: 
In the BIOS go to the hd section and look, what the BIOS think the
speed of your hd is (3 GB/s or 6GB/s). When found directly set you
SATA chip to that speed. It is recommended to do so by the help of
text of my BIOS. I have a 3GB/s disk. And yes, IDE is ok.

Here you can find explanations about AHCI vs. IDE sata mode.
http://www.techarp.com/showfreebog.aspx?lang=0&bogno=316

On my board (ASUS Crosshair IV Formula) it was said, that AHCI is
slower than IDE, but (!) is not due to IDE vs. AHCI but to a
limitation of the chip.

Look at the benchmarks above: There no place to go faster than that.
3/6 GB/s on cach read are standard compliant and ~100 MB/s is the
limitation of hardware normal people like you and me can pay for.

Plug on the front:
This seems to be E-Sata jack AND SHOULD BE CONNECTED INTERNALLY ONLY
TO AN E-SATA (not SATA) JACK ON THE MOBO.

In unmounted status: Yes it should be hotpluggable as USB. BUT dont
connect the E-SATA jack of the case to a normal SATA jack on the
board!

E-SATA != SATA !!!!

HTH
mcc