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 Post subject: Adding some Cage and disks.
PostPosted: Wed Dec 27, 2017 7:09 pm 
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Joined: Wed Feb 17, 2016 8:46 pm
Posts: 15
Hi 3PAR guys,

I am in a way to extend some 3PAR, adding cage and disks.
A question come to me : My initial config is a simple 3 CPG, one for each type of disks. So I have 1 CPG for SSD, 1 CPG for FC SAS 10K and 1 CPG for NL 7.2k, driven by AO.

I want to add storage to these CPG, May I stick to the kind of disks that were used before ?
For exemple FC disks were only 450Go SAS 10K initially. I understand that I should stick to 10K rpm but is it recommended / mandatory / prohibited / permitted / to mix type of disk ? may I add some 900 Go (10K) to this very same CPG ?

thank you all for your comments.

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3 x 3PAR 7200 / OS 3.2.1


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 Post subject: Re: Adding some Cage and disks.
PostPosted: Thu Dec 28, 2017 7:28 am 

Joined: Mon Sep 21, 2015 2:11 pm
Posts: 489
900GBs are no longer available as far as I know.

Keep in mind that putting 900GB 10k and 450GB 10k drives within the same CPG you will always have a higher percent used space on the 450GB as 3PAR will fill chunklet by chunklet. Also remember that a 450GB 10k drive has a higher IOPS per GB ratio than the 900GB 10k drives. So if you keep your IO density the 900GB drives will be hit by 2x the IOPS (when filled) compared to the 450GB drives. If your 450GB drives is nowhere near to its limits it might not be any issues... if you are at 90% load on your 450GB drives today, adding a larger disktype could be a disaster if the data you plan to add has the same IO load as the existing one.


Best practice states that it is supported to mix different size as long as the biggest drive is not larger than 2x the size of the smallest disk in the CPG. But as always best practice is what fits most scenarios and it not a guarantee to be the best option in your scenario.

So what I'm trying to say... the safest thing is to grow with what you already have. If those drives are no longer available it is in almost every case okay to go one size bigger.


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 Post subject: Re: Adding some Cage and disks.
PostPosted: Thu Dec 28, 2017 10:38 pm 
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Joined: Wed Feb 17, 2016 8:46 pm
Posts: 15
Thanks MammaGutt for your constructive comments.

Have all an happy new year celebration.

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3 x 3PAR 7200 / OS 3.2.1


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