HPE Storage Users Group :: View topic - Adding more disk to my system

Hi Folks!

i have a doubt, right now i have a 3par 7450 with 24 SSD

8 disk 1.92TB
16 disk 480GB

We are using a CPG Raid 5 (3+1), and now are are looking for adding new disk, so here is my doubt.

I want to buy 6 disk of 1.92TB, but the HPE seller is telling me that is a bad practice, i should buy 8 disk of 1.92tb regarding to the Raid configured in the CPG, i asked why, because the raid is performed with chunklets, not the entire disk as legacy systems but i have no answer.

I was wondering if you guys can help me with disk, those disk are very expensive.

Best Regards!

Author:	seeeking [ Tue Mar 20, 2018 10:10 am ]
Post subject:	Adding more disk to my system
Hi Folks! i have a doubt, right now i have a 3par 7450 with 24 SSD 8 disk 1.92TB 16 disk 480GB We are using a CPG Raid 5 (3+1), and now are are looking for adding new disk, so here is my doubt. I want to buy 6 disk of 1.92TB, but the HPE seller is telling me that is a bad practice, i should buy 8 disk of 1.92tb regarding to the Raid configured in the CPG, i asked why, because the raid is performed with chunklets, not the entire disk as legacy systems but i have no answer. I was wondering if you guys can help me with disk, those disk are very expensive. Best Regards!

Author:	ailean [ Tue Mar 20, 2018 10:58 am ]
Post subject:	Re: Adding more disk to my system
From the quickspec docs Quote: Minimum upgrade quantity is 4 drives per node pair or 2 drives per enclosure, whichever is larger. So on a 4 node system, if you don't have any expansion shelves, it'll be 4 drives x 2 node pairs = 8 drives. Beyond that you always have to add drives in pairs to each shelf so I guess you could do 8, 12, 16 etc. drives in one upgrade. It is the drawback of larger drives, upgrading less often but more expensive purchase (it is cheaper/GB though).

Author:	MammaGutt [ Wed Mar 21, 2018 2:18 am ]
Post subject:	Re: Adding more disk to my system
seeeking wrote: Hi Folks! i have a doubt, right now i have a 3par 7450 with 24 SSD 8 disk 1.92TB 16 disk 480GB We are using a CPG Raid 5 (3+1), and now are are looking for adding new disk, so here is my doubt. I want to buy 6 disk of 1.92TB, but the HPE seller is telling me that is a bad practice, i should buy 8 disk of 1.92tb regarding to the Raid configured in the CPG, i asked why, because the raid is performed with chunklets, not the entire disk as legacy systems but i have no answer. I was wondering if you guys can help me with disk, those disk are very expensive. Best Regards! The quick and dirty answer.. With 16 disks you can write 4 full stripes, while with 14 you only get to write 3 because the two last drives in the final stripe is busy writing one of the other 3 stripes. So it is only a performance related best practice.

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