sony-vaio-z-series team mailing list archive

["K. Posern" <quickhelp@xxxxxxxxx>]

Hi Joel,

thanks for your answer. Because in your example you were speaking about
md0 I thought it was a somewhat different setup.

I really like the mdadm approach that basically unmaps the fakeraid for
you via the md127 and then gives you a normal disk to play with (md126)
:) ... I don't like the naming of dmraid.

But as you said it is handled transparently like a (true) linux software
raid --> hence you can use all the (e.g. monitoring) infrastructure of
an mdadm linux software raid :)

Knuth

---

On 12/02/2010 04:37 PM, Joël Bourquard wrote:
> Hi Knuth !
> 
> Well actually I believe you have exactly the same setup as me.  And it
> *is* a linux software raid - it just happens to be setup with the
> parameters read from the Intel fakeraid metadata that is on the disks.
> But the operation is fully software.
> 
> /dev/md126 is the linux software raid, which uses /dev/md127 as the
> underlying interface to the metadata.  You can see that in /proc/mdstat:
> 
> md127 : inactive sdd[3](S) sda[2](S) sdb[1](S) sdc[0](S)
>       9028 blocks super external:imsm
> 
> But /dev/md126 is really a true linux software raid0, with a 128kB
> stripe size.
> 
> Yes, many distros (including Gentoo also) still use initrd's which don't
> include mdadm 3.0+, which is required to handle the intel metadata.
> That's why I recommend to copy a static compile of it, to the initrd.
> 
> Best regards,
> 
> Joël
> 
> 
> On Thu, Dec 2, 2010 at 9:31 PM, K. Posern <quickhelp@xxxxxxxxx
> <mailto:quickhelp@xxxxxxxxx>> wrote:
> 
> 
>     Hi Joel,
> 
>     Thanks for the report.
> 
>     I ca add though:
> 
>     If you use mdadm instead dmraid to access your NATIVE fakeraid (without
>     a linux software raid) you get actually the same results :)
> 
>     hdparm -tT /dev/md0
> 
>     /dev/md126:
>      Timing cached reads:   9010 MB in  2.00 seconds = 4506.74 MB/sec
>      Timing buffered disk reads: 1498 MB in  3.00 seconds = 498.81 MB/sec
> 
>     And a little side remark:
> 
>     For all I know: mdadm is also favored by intel going forward over dmraid
>     - but ubuntu still favors dmraid by default (I think).
> 
>     Best,
> 
>     Knuth
> 
>     On 12/02/2010 12:42 PM, Joël Bourquard wrote:
>     > Actually I think buffered reads are the same, it's just some
>     measurement
>     > variance that we see here :-)
>     >
>     > I noticed a major improvement when launching huge apps (firefox,
>     > evolution, OpenOffice) for the first time, and of course when
>     copying files.
>     >
>     > Other than that, the general speed of the system was already very
>     high -
>     > so it's difficult to rule out the placebo effect. But it's
>     certainly not
>     > running any slower than before, far from it! And numbers are
>     consistent.
>     >
>     > Best regards,
>     >
>     > Joël
>     >
>     > --
>     > Sent from my Android phone.
>     > Please excuse my brevity.
>     >
>     > On Dec 2, 2010 6:31 PM, "Simon Brown" <lists@xxxxxxxx
>     <mailto:lists@xxxxxxxx>
>     > <mailto:lists@xxxxxxxx <mailto:lists@xxxxxxxx>>> wrote:
>     >
>     >
>     >
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