Dell Perc 710 -vs- LSI9207 (pass through -vs- queue depth)

[terrible_towel]

Hello,

I'm got some demo R720's from Dell with Perc H710's in them.  This card does not support pass through mode, so I had to create 16 separate 1 disk raid 0 'arrays' (2 SSD, 14 HD).  I believe vSAN will be able to use them (once I tag the SSDs as SSDs).   These were spec'ed from Dell as vSAN ready nodes, so I was surprised to find the Perc card does not support pass through.  I asked Dell.. and since these are demo boxes that I can send back, they want to send me the LSI9207 that does support pass through.

The Perc H710 has a queue depth of 1024.

the LSI9207 has a queue depth of 600.

Is getting true pass through worth giving up half the queue depth?

I've looked for guidance on how to configure the raid 0 arrays with the Perc card to best support vSAN.. but have not found anything at all.

Any guidance??

Thanks,

Paul

[tehkuhnz]

From what I have read/heard using the Perc H710 in Raid 0 mode will be more beneficial than using a pass through HBA.( Larger queue depth and there seems to be more of push to get away from pass through) I could be wrong, but if you are using a dell you would be better off with the H710 or H710P. However, both cards appear on the HCL so theoretically you should be fine either way .....

[depping]

tehkuhnz wrote:

From what I have read/heard using the Perc H710 in Raid 0 mode will be more beneficial than using a pass through HBA.( Larger queue depth and there seems to be more of push to get away from pass through) I could be wrong, but if you are using a dell you would be better off with the H710 or H710P. However, both cards appear on the HCL so theoretically you should be fine either way .....

I would not say there is a push to get away from passthrough. personally I feel passthrough provides a better operational experience.

[DrewDeM]

I would not want to lose VSAN functionality and use RAID 0 if I could help it as long as I wasn't crippled by a low queue depth

Duncan's article should help shed some light on this.

http://www.yellow-bricks.com/2014/06/09/queue-depth-matters/

Duncan is there a good rule of thumb formula to figure out the queue depth you should look for in a controller based on the drive count and drive type?

[kirand]

Apart from hot plug and unplug of the drives, you will not lose any VSAN functionality with RAID-0 mode.

Text from VSAN HW Guidance doc

"Pass-through and RAID 0 performance for the same storage controller should be similar in most instances

within a Virtual SAN solution. The supported storage controller queue depth is the most important factor in

determining storage controller performance in a Virtual SAN solution"