Software RAID 5 or something else?

[Seann Clark]

aragonx at dcsnow.com wrote:
> Hello all,
>
> I had a drive failure a few months back so I decided it was time to rework
> my home server's storage.
>
> Now I have 5 750GB SATA dives and now I need some advice on how to set
> things up.
>
> My original idea was to put them in a RAID 5 configuration.  This sounded
> good until I started researching RAID controller cards.  It looks like it
> will cost me $520 to get a good PCI-E card (3Ware 8 port).  I don't think
> I want to spend that much if I don't have to.
>
> My goals are two fold.
>
> 1) I want to get some redundancy in case of a drive failure.
>
> 2) I want to increase my performance.  I have benchmarked my read and
> write performance to and from this server.  Using Samba, I seem to be able
> to get about 50Mb/sec reads and 40Mb/sec writes.  I am on a gig network
> and would like to be able to max out the cards (90Mb/sec is what I get at
> work).
>
> So, the question is, what should I do?
>
> 1)  Bite the bullet and get the hardware RAID controller.  Will this give
> me the performance I want?
>
> 2)  Go with a software RAID 5.  Will I lose performance with this
> configuration?  If I use this but only get modest performance gains, that
> would be acceptable.
>
> 3)  Go with some other software RAID level.
>
> Any help would be appreciated.
>
> ---
> Will Y.
>
>
>
>   
Will,

    I can't help with the software side, but I have a 3ware 8 port 
myself and here are the stats I am getting from my RAID 5:

(output of tw_cli)
Unit  UnitType  Status         %RCmpl  %V/I/M  Stripe  Size(GB)  Cache  
AVrfy
------------------------------------------------------------------------------
u0    RAID-5    OK             -       -       64K     3259.56   OFF    ON

Port   Status           Unit   Size        Blocks        Serial
---------------------------------------------------------------
p0     OK               u0     465.76 GB   976773168     WD-WMASYXXXXX
p1     OK               u0     465.76 GB   976773168     WD-WMASYXXXXX
p2     OK               u0     465.76 GB   976773168     WD-WMASYXXXXX
p3     OK               u0     465.76 GB   976773168     WD-WMASYXXXXX
p4     OK               u0     465.76 GB   976773168     WD-WCAS8XXXXX
p5     OK               u0     465.76 GB   976773168     WD-WCAS8XXXXX
p6     OK               u0     465.76 GB   976773168     WD-WCAS8XXXXX
p7     OK               u0     465.76 GB   976773168     WD-WCAS8XXXXX

Name  OnlineState  BBUReady  Status    Volt     Temp     Hours  LastCapTest
---------------------------------------------------------------------------
bbu   On           No        Testing   OK       OK       0      24-Nov-2008





Timing Statistics:

/dev/sda:
 Timing cached reads:   11640 MB in  2.00 seconds = 5830.68 MB/sec

/dev/sda:
 Timing buffered disk reads:  152 MB in  3.00 seconds =  50.64 MB/sec




my biggest bottle neck right now is the write-cache is off due to a 
battery test that is being done. Total cost for the card (and battery 
backup) was about 575.00. The card, from new egg is 
http://www.newegg.com/Product/Product.aspx?Item=N82E16816116054


Another note, 3ware has good support in Linux, and is very nice and easy 
to manage if you do go that route. I will leave it to the 
DMraid/software RAID guys to answer for that though


~Seann

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