[Lustre-discuss] LUN reassignment DDN and OSS

[Kit Westneat]

Hi Syed,

If I'm not mistaken, Lustre uses a 4k block size anyways, so I don't 
think there is even a space penalty for going to 4k blocks. Due to the 
physical 512b sector size for the disks, 4k blocks also means that the 
s2a never has to do any unnecessary reads to complete a write. So all 
around 4k is the way to go.

You might want to rezone them just to make sure, also try reloading the 
FC driver/rebooting to make sure that the HBA has rescanned the bus.

Thanks,
Kit

syed haider wrote:
> All,
> I recently raised a question about unbalanced OSTs and received the 
> right answer - increase the size of the OSTs. So I set forth to do this on
> our DDN controllers and rather than having 32 1TB LUNs i decided to go 
> with 4 8TB LUNs instead. In doing this I learned our LUNs were created
> with the default 512 size and from reading the manual it appears it 
> would improve performance for our work to go with 4096. Since most 
> jobs run
> on lustre would be creating larger files (sequential) we're not 
> concerned about losing space from smaller files taking up a 4k block. 
> Is there any other concern I should have
> with going with the larger block size?
>
> Second question for the DDN expert- We have 4 OSS's connected to DUAL 
> DDN 9550 controllers via fiber. With the older configuration we had
> one 1TB LUN using one Tier so the lun output looked something like this:
>
>          Logical Unit Status    
>
>                                          Capacity  Block
>  LUN  Label        Owner  Status         (Mbytes)  Size  Tiers Tier list
> -------------------------------------------------------------------------------
>   0 lun 0            1    Ready            1120098   512    1  1
>   1 lun 1            1    Ready            1120098   512    1  2
>   2 lun 2            1    Ready            1120098   512    1  3
>   3 lun 3            1    Ready            1120098   512    1  4
>   4 lun 4            1    Ready            1120098   512    1  5
>   5 lun 5            1    Ready            1120098   512    1  6
>   6 lun 6            1    Ready            1120098   512    1  7
>   7 lun 7            1    Ready            1120098   512    1  8
>   8 lun 8            2    Ready            1120098   512    1  9
>   9 lun 9            2    Ready            1120098   512    1  10
>
>
> After making the change to only 4 LUNs two of my OSS's don't see any 
> SCSI devices when i run fdisk. By deleting and recreating the luns did 
> I somehow cause
> a zoning issue? Thanks in advance.
>
> Syed


-- 
---
Kit Westneat
kwestneat at datadirectnet.com
812-484-8485