[mythtv-users] Question re: available SATA ports and linux software RAID

Simon Hobson linux at thehobsons.co.uk
Thu Apr 7 08:28:20 UTC 2011


Bobby Gill wrote:
>Going to be setting up a server soon, am pretty settled on RAID5 
>linux software RAID. I currently have an ASUS P5K-E mobo that has 6 
>SATA slots + 2 eSATA slots. I would be using 1 drive for my Arch OS, 
>so that leaves 7 available slots for my array.
>
>My question is, what if I would wish to have a 8/10/12 drive array 
>either right off the bat or in the future? Would getting one of 
>these work: 
>http://www.newegg.com/Product/Product.aspx?Item=16-101-358
>
>That would add 8 SATA slots. I am just trying to confirm that adding 
>that card (or one like it) would do the trick of adding SATA slots 
>and could be used as any other SATA slots for linux software RAID, 
>so I wouldn't have to worry about not being able to physically add 
>drives to my array in the future if desired.
>
>(I was considering the HighPoint 2300 PCIe controller card but after 
>communicating with their web support, they confirmed to me that 
>multiple controller cards of theirs (any?) cannot be used in 
>conjunction to form an array (one card = 4 slots so I couldn't buy 2 
>cards and build an 8 drive array on the same mobo).)

OK, I think there is some confusion there.

The Supermicro card you link to is a SAS RAID card - and using it's 
inbuilt RAID controller will only do the drives connected directly to 
it. It's overkill because if you are doing software RAID then you 
won't be using any of the on-card facilities.

As for the Highpoint, again I suspect they are talking about using 
on-card RAID, and for that you can only use the drives attached to 
the card. Again, if you are doing software RAID then you don't need 
the on-card RAID.

So for software RAID you do *NOT* need expensive RADI controllers, 
just just need plain SATA controllers.

For large storage, you may find this article an interesting read :
http://blog.backblaze.com/2009/09/01/petabytes-on-a-budget-how-to-build-cheap-cloud-storage/

I suspect some of the comments about choice of host adapters are out 
of date, but it does give you an insight into some of the issues 
involved.

-- 
Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.


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