Very little responses.
The geenral concensus was to do scheme A as it utilises the full bandwidth
of your available I/O controllers and to configure your storage subsystems
to present devices (logical disks) on LUNs spread on different I/O paths to
the host. Creating a large device and prsenting it to just one I/O path will
utilise just that I/O path's bandwidth. The exception of course is if one is
using FC-AL I/O controllers in which case scheme B would prove most optimal.
> -----Original Message-----
> From: Caparrosso, Nelson T.
> Sent: Wednesday, April 26, 2000 10:03 AM
> To: 'firstname.lastname@example.org'
> Cc: 'email@example.com'; 'firstname.lastname@example.org';
> Subject: Storage Subsystems: Optimal Configuration
> Revered Gurus,
> As we all know, Storage Subsystems (EMC, Sun, HP, etc) can be configured
> to present its RAID storage to a UNIX host as logical disks sized as
> appropriate to I/O channels (SCSI or FC-AL). I have been facing a blank
> wall of sorts from storage vendors - which is an optimal configuration to
> get good I/O bandwidth and better subsystem cache (nvram) utilisation. My
> inquiry, which of the following two schemes would give me better
> I/O Channels are UW-SCSI at (20~40 mbps), UNIX host with 8 I/O channels,
> Filesystems via LVM
> Storage Subsystem is 256 Gb RAID-0+1, with 8 GB Cache, 8 UW-SCSI I/O ports
> Scheme A:
> Subsystem is configured to present 64 - 4 GB Disks to the host on 8 I/O
> Channels with each channel allocated 8 x 4 GB disks. Host is then
> configured to have have striped filesystems built on disks accross the 8
> I/O channels (Controllers)
> /filesys1 --- a stripe of disk1 on controller 1 + disk 2 on controller2
> ... so on to controller 8, creating a 32GB filesystem
> /filesys2 --- a stripe of disk 9 on controller 1 + disk 10 on controller
> 2 ..... etc.
> Scheme B:
> Subsystem is configured to present 8 32 GB Disks to the host on 8 I/O
> channels with each channel allocated the 32GB logical disk. Host is then
> configured to have filesystems built with each having the lone 32 GB disk
> from the subsystem on each own controller.
> /filesys1 -- disk1 on controller 1 ~ 32 Gb
> /filesys2 -- disk2 on controller 2 ~ 32 Gb ... so on
> The question really is it is advantageous to configure a storage subsystem
> to present disk devices to a UNIX host as large disks to be dedicated to a
> single controller or configure as smaller disk devices distributed among
> several I/O controllers and use host LVM to create large filesystems?
> Thanks for any feedback, thoughts.
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