Trying to build 7-45 TB storage on the cheap with only Dell hardware

Mark Watts m.watts at eris.qinetiq.com
Mon Jun 2 10:52:53 CDT 2008


On Monday 02 June 2008 14:34:25 bert hubert wrote:
> Hi everybody!
>
> I hope you can help us - I am already talking to my account manager, but I
> think the Linux perspective is better on this list.
>
> I am looking for a storage solution, a DAS with a "flexible" growing
> capability from 7 to 16, and possibly 45 TB.

Sounds like you need to use LVM then.

> As I am trying not to spend too much money, I am hoping to see if we can
> let Linux do a lot of the heavy work so I don't need to get a NAS or a
> SAN.
>
> For convenience sake, I only want to use Dell hardware as this is easily
> supported, and I don't want to trawl the web for separate solutions.
>
> My storage needs are mostly very large files, so I don't need a lot in the
> way of dedicated filesystems.
>
> The MD1000 seems promising, but will it do what I want? It seems to be a
> great not too expensive solution, a bunch of disks for storage, connected
> to a machine, or two machines, let Linux do the work, there you go.
>
> Do the individual disks show up (/dev/sda, sdb sdc etc)? Or does the
> controller already convert the disks into huge devices? Either is fine with
> us, I have good experiences with md-support in Linux.
> In other words, a 'dumb container of disks' would also be fine by me - but
> the MD1000 appears to do more. If a 'dumb container of disks' is available,
> which one works best?

The MD1000 is simply a box of disks; each disk being presented separatly to 
the Operating System.
Traditionally, you'd also buy a PERC RAID card to do the heavy-lifting of 
turing a bunch of disks into a RAID array.

Looking at the product specs for the MD1000, you can daisy-chain an additional 
2x15 disk enclosures giving you 45TB raw storage.
You'd then RAID this up in some way on the PERC card.
Note: The PDF spec sheet says you can only have upto 30 drives in a single 
RAID group, so you're unlikely to be able to have all 45 drives in a single 
logical device.

>
> Some more questions:
>
> - Which card is needed in the poweredge servers to connect to the Dell
> MD1000? A secondary perc6e sas raid controller card or a perc5e sas raid
> controller card or something else?

PERC 5/E supports RAID levels 0, 1, 5, 10 and 50
PERC 6/E supports RAID levels 0, 1, 5, 10, 50 and 60

> - In a 7/8 split configuration with a second EMM in the MD1000, what kind
> of card and cables do I need in the server(s)?

On PERC card per server.

> - With a second EMM in 7/8 split configuration (to separate servers) do you
> get 2 connections of each 4 * 3 Gbps or two connections of each 2 * 3 Gbps?
> In other words is the backend of the MD1000 capable of acting like two
> individual MD1000, each filled with only half the disks?
>
> - To be sure, is the size of the 7/8 split configuration expandable by
> adding a secundary MD1000?

Not sure - the spec sheets don't go into this detail.

> - Do you have any additional tips and tricks for the MD1000 - how to get
> Linux to work with it to get the best performance.

If you use the PERC card to do the array management, you should just see a 
single very large device.
You may need to use LVM directly on the device in order to use it as one 
filesystem, and you may need to use a 64bit OS in order to format it.

Mark.

-- 
Mark Watts BSc RHCE MBCS
Senior Systems Engineer
QinetiQ Applied Technologies
GPG Key: http://keyserver.veridis.com:11371/search?q=0x455420ED
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