ML350G6 , P800 , 16disks , 1 logical drive

[PAPADOPOULOS G.]

Hello,

Could anyone please help with this ?

A customer has a ML350G6 (487928-xx1)with an optional second drive cage (507803-B21), 16x146GB sas disks (512547-B21)and a P800 array (381513-B21).
He wants to create 1 logical drive (raid 5) with all the disks.
Is it possible to connect each cage to different controller channel and make only one array with all the disks ?

thanks
giannis

[TTr]

It may be possible but it would not be supported. You connect the internal connectors to the first cage as expected and find the right cable and connect the external connectors back inside the server through a slot opening to the second cage. I would not recommend it since not only it is not supported, you might not get the expected i/o from a 16-disk raid5 drive.

[PAPADOPOULOS G.]

I think that P800 has 2 internal & 2 extrenal channels
Is it possible to connect each internal channel to each drive cage and make an array with 16 disks ?

thanks again
giannis

[TTr · Accepted solution]

Each internal channel has only 4 SAS ports so you need both internal channels for the first 8 disks in the first disk cage.
Take a look at the quick specs for the P800 for details. http://h18004.www1.hp.com/products/quickspecs/12616_div/12616_div.html

You would need to find a SAS expander and make it work internally to be able to spread one x4 channel to 8 ports/disks for the first cage and the same with second channel.

The reason that it is claimed in the specs that the P800 can support 108 disks is via its external connectors and the daisy-chaining external enclosures together (msa50 or msa60). The external MSA enclosures have the port expanders built in. See Question8 in http://h18004.www1.hp.com/storage/disk_storage/msa_diskarrays/drive_enclosures/msa60/qa.html?jumpid=reg_R1002_USEN

There is SAS expander card that seems to be doing what you need but that is only available for the P410 controller http://h18004.www1.hp.com/products/servers/proliantstorage/arraycontrollers/sas-expander/index.html

Keep in mind that the expanders do allow you to connect a large number of drives to one port (or a small number of ports) in a identical setup to a LAN switch. So from an i/o perspective if you use the drives sporadically, a few drives at a time, i/o will be acceptable. In a RAID5 setup all 16 drives have to be read concurrently so that the raid5 stripe can be generated and passed to the server. Can you imagine the i/o impact if all 16 drives are connected NOT to 16 separate ports on the controller but to 4 or 8 ports only. You would never be able to get decent i/o.

[PAPADOPOULOS G.]

Your answer was most helpfull

Thanks again
giannis

[PAPADOPOULOS G.]

Above answers was most helpfull