[SATLUG] was now help with raid setup on linuxmce box now linuxmce success

John Pappas j at jvpappas.net
Wed Oct 1 13:49:12 CDT 2008


On Sun, Sep 28, 2008 at 21:32, Todd W. Bucy <toddwbucy at grandecom.net> wrote:
<<SNIP>>

> while this did work and linuxmce installed just fine I found the overall
> performance to be lacking.  In particular when I tried to transfer over
> 150 gig's of media from a samba share in my home office it took 4 1/2
> hours.  (Mind you that this was not a wireless transfer but ethernet.)


I assume the array was done building when you were testing, otherwise the R5
would have been artificially slow due to the contruction I/O and XOR
calculations.  R1 will almost always be faster than R5, since R5 requires
CPU XOR calculations and double I/O, where R1 only requires double I/O.

If you are going to be transferring a lot of video (Especialy HD), I
recommend going to GigE.  A 5 port 1000Mb switch runs <$50 and a GigE Nic is
<$30 (If not already built-in).  Transfers run about 1.5GB/Min for me (FTP
-> 4x SW RAID5), so your 150GB would have taken about ~15 Min.

<<SNIP>>

I finally settled on doing the following:
> SDx 5 gig RAID1 swap
> SDx 495 gig RAID1 LVM
> SD 320 gig hd RAID1 LVM
>

I don't see a Boot partition, and you cant boot off of LVM, so I must be
missing something.  I hope that your 2x LVM md devices are in different
VG's, otherwise you are either concatinating or striping across the md's.
That is fine, as in your case, you would have to sustain an md (2 drives,
same array, granted).  If you are going to do that, I recommend striping
across the 2 R1's.  You will have to specify a `-i 2` during the LV
creation, so that the LV is striped across the 2 PVs.  That would be even
faster, since the streams will be alternated over both R1 arrays, rather
than on one or the other.


> In the end this gave me 815 gig of / upon which to install LinuxMCE.
> Performance wise the same transfer took a little over three hours.  Yeah
> I lost space (over 100 gig) but I think that I gained a pretty
> substantial performace boost.
>

That is the RAID tradeoff, Speed or Space.  I also hope that the arrays were
done building when you tested, as the performance hit of the rebuild would
again artificially hinder performance (Not as much as a R5 rebuild, but
still noticeable).


> I also found a new use for my nokia770, Its now the best damm remote
> control that I have ever had the pleasure of channel surfing with.


I bet.  That sounds cool.  You could also transcode and store video on the
770, so that you can watch other stuff on the "remote" too!


> To make it more challenging two of the machines will be laptops (I foresee
> problems with wifi) and the third will be run on on a custom built useing
> virtualbox.


I have not had any problems with video over wifi (once I found the cleanest
freq's and added some gain with better antennae).  I do have 2 different
WLANs on 2 different (non-neighboring) freq's in the house, one is dedicated
to my 3 laptop computers, the other is for the 3 video clients.  A, G, or N
should do fine.  B is FAR too slow for any type of higher-quality video.

wish me luck


Luck favors the prepared, so you will be fine.

HTH,
jp


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