[Beowulf] Problem with Single RAID disk larger than 2TB and Linux

Joel Jaeggli joelja at bogus.com
Sat Oct 6 15:09:17 EDT 2007


Guy Coates wrote:
> Luns over 2TB are a bad idea. There are just too many reasons why they might not
> work, and trying to track down the right one is a pain.
> 
> Your workaround to use the LVM to stripe 3x1TB luns together is the way to go.
> (You really want to use LVM anyhow, as  trying to do SAN storage without it is a
> pain.)
> 
> You've covered the usual Gotchas with 2TB luns (dos partition tables and 32 bit
> kernels),  so I'd suspect your storage array.  Check with Hitachi that the array
> supports creating luns over 2TB. Many don't, and for maximum confusion, some
> allow you to create >2TB luns, even though you  can't subsequently use them.

I have at least two disk arrays that will assemble units greater than
2TB but have to export them as multiple luns... Some of these controller
designs are quite old despite being in newish (fibre-channel-sata
enclosures) this is all seems to stem internally from their using 32 bit
signed intergers for block count.

(the more things change the more they stay the same)

My approach (we designed it this way from the outset) was to assemble
2TB raid-6 stripes into a single 12TB volume using LVM (this was back in
the era of 500GB drives).

> Cheers,
> 
> Guy
> 

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