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 Post subject: Re: Mix different drive sizes on 3par 7200
PostPosted: Fri Oct 20, 2017 12:05 am 

Joined: Fri Oct 20, 2017 12:01 am
Posts: 1
Hi All,

Whats the conclusion here. How can we over come this issue of over stressing the 4TB disks ?

Thanks In Advance
-Raj


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 Post subject: Re: Mix different drive sizes on 3par 7200
PostPosted: Fri Oct 20, 2017 3:27 am 

Joined: Mon Sep 21, 2015 2:11 pm
Posts: 457
gujjula wrote:
Hi All,

Whats the conclusion here. How can we over come this issue of over stressing the 4TB disks ?

Thanks In Advance
-Raj


Simple, don't mix different sized drives in the same tier/CPG. For SSDs the penalty is less (because the SSDs is usually not the limiting factor), for NL the penality is usually substantial because of the amount of data stored there and the very low amount of IO which the drives are capable of producing.

Best practice (last time I checked) stated that the largest drive should never be more than 2x the size of the smallest drive in the same CPG. Best practices are general recommendations and for some environments and drive types, 4x size is not a problem, for others even 2x could be a huge problem.


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 Post subject: Re: Mix different drive sizes on 3par 7200
PostPosted: Fri Oct 20, 2017 1:54 pm 

Joined: Fri Oct 20, 2017 1:45 pm
Posts: 2
Hello,

I'm new to this forum and relatively new to the 3par. I inherited 2 3pars at my place of work, and I have received a notice that HP is discontinuing a number of drives including mine. The new drive replacements are twice the size of our current HCBRE0900GBAS10K (900GB) drives. My question is once my current drives start failing and I get these new larger drives to replace them I will be introducing 1 larger drive at a time. I don't think this is a good idea from the information in this thread; however, I don't really know another way around this outside of purchasing all new drives and that is cost prohibitive. Does anyone here have any suggestion on what I should consider doing here?

Thanks,
Scott


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 Post subject: Re: Mix different drive sizes on 3par 7200
PostPosted: Sat Oct 21, 2017 2:52 am 

Joined: Mon Sep 21, 2015 2:11 pm
Posts: 457
My understanding is that the 1.2 TB will still continue.

1.2 TB drives together with 900GB drives wouldn't make that big of a difference. If you suddently loose 10+ drives and get replaced by 1.2TB you might see issues when your array is so full that you're only accessing the 1.2TB drives, but in that case you are using space you didn't pay for in the first place.


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 Post subject: Re: Mix different drive sizes on 3par 7200
PostPosted: Mon Nov 06, 2017 12:18 pm 

Joined: Fri Oct 20, 2017 1:45 pm
Posts: 2
I have been reading the 3par 7400 documentation and it states that you should add 8 drives at the same time of the same size. Is this in regards to new drives (Expansion) and not replacement drives?

Thanks,
Scott


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 Post subject: Re: Mix different drive sizes on 3par 7200
PostPosted: Mon Nov 06, 2017 12:52 pm 

Joined: Thu Jul 06, 2017 3:28 pm
Posts: 23
ScottG wrote:
I have been reading the 3par 7400 documentation and it states that you should add 8 drives at the same time of the same size. Is this in regards to new drives (Expansion) and not replacement drives?

Thanks,
Scott


Correct, that is for adding expansion disks. Replacement drives are still done one at a time.


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 Post subject: Re: Mix different drive sizes on 3par 7200
PostPosted: Mon Nov 06, 2017 1:28 pm 

Joined: Mon Sep 21, 2015 2:11 pm
Posts: 457
ScottG wrote:
I have been reading the 3par 7400 documentation and it states that you should add 8 drives at the same time of the same size. Is this in regards to new drives (Expansion) and not replacement drives?

Thanks,
Scott

I think this is from the "era" from when the 7k was released, spinning media was the thing, R5 3+1 was used by most and everyone wanted HA cage. You always need to add disks in pair and you need 4 cages for 3+1 HA.


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