Limitation in store profiles maximum drives in a pool

Question

Hi, In an Unity 300 I have 18 * 1.8 TB and 20 1.2 TB Drives (Excluding system drives which are 4 other 1.2 TB) And I have a strange problem While creating a RAID 5 out of my 1.8 TB disks it allows only 14 disks while we have 17 available (one goes for spare) so this makes at least two drives unusable making me loss about 3.5 TB of space. Meanwhile there is no limitation on 1.2 Disks. I can choose 19 out of 20 .. What is this limitation and how can I solve my problem. Thanks

Rainer_EMC · Answer

sounds strange see the Unisphere Online Help for a list of support RAID configurations If you are sure you selected maximum capacity and it still doesnt work then please open a service request

MdGanji · Answer

You know man every day I'm finding strange things in unity.

And yes I'm sure I'm selecting the maximum capacity fir strip length

And when I run /stor/config/profile -configurable show It also says that you can choose 14 of 18 in a RAID 5 with maximum capacity. Also I tried to create pool with command and choose more than 14 but it was created using again only 14 disks and I'm loosing my expensive (very expensive) disk space

Finally you can see that I have 18 X 1.8 TB disks.

ID	= dg_24
	Drive type	= SAS
	FAST Cache	= no
	Drive size	= 1772662276096 (1.6T)
	Vendor size	= 1.8T
	Rotational speed	= 10000 rpm
	Number of drives	= 18
	Capacity	= 31907920969728 (29.0T)
	Recommended number of spares = 1

So Rainer Are you from EMC support team? Can you escalate this ? How can I open a service request? I'm just a customer not a re seller ..

Rainer_EMC · Answer

Hi,

no I am not from support

this forum is not a replacement for customer service - its a community forum.

You can open a service request via phone, web, customer service chat,... - all available on support.emc.com

Regarding capacity I would suggest to talk to the Dell EMC or partner that sold you the system - he should have done a config according to your capacity needs.

For R5 the support raidgroup sizes are 4+1 or 8+1 or 12+1

for HDD there are no smaller or fractional raidgroups possible

so 18-1 drives dont make much sense - I would suggest to get one more 1.8TB drive

regards

Rainer

MdGanji · Answer

Thanks Rainer, no problem, I will get another 1.8TB but while it does not accept more than 14 drives for a RAID 5 of these 1.8 disks so what will be in that purchase ?

MdGanji · Answer

Your math is correct Rainer.. It goes this way : (8+1)+(8+1)+1(Forced spare)

BUT

It does not work ..

It does work with my 1.2 TB disks just the same way (I can choose 16 of 18 or 18 of 20 without any problem)

but for my 1.8 TB disks it just doesn't go up from 14 ..

I know it sounds weird but believe me it is true.

And the 1.2 TB disks are just the same as 1.8 disks (10k) .. They're just 1.2 TB

Rainer_EMC · Answer

with 18 drives you can configure 2x 8+1R5 if my math is correct IF you talk to your seller he should be able to run a sizing tools and show you exactly how much capacity you can get for your config

Rainer_EMC · Answer

how about first adding 9 drives and then another 9 ?

if this doesnt work then please open a service request

a comment on a community forum like this will not get code fixed.

That needs a service request where customer service checks the issue and if necessary passes it as a bug to engineering to fix

MdGanji · Answer

Nothing, They're just killing time

Rainer_EMC · Answer

what response did you get from your service request ?

kelleg · Answer

What is the code version of the UNity array? Are you running 4.2.x? In that version they introduced the Dynamic Raid which has different rules for the number of disks in the Pool for different stripe widths. If you are running 4.2, you might to look at the docu85573_Dell-EMC-Unity--Dynamic-Pools---Overview.pdf

https://support.emc.com/docu85573_Dell_EMC_Unity:_Dynamic_Pools_-_Overview.pdf?language=en_US

glen

MdGanji · Answer

I'm choosing the strip as mixed and number of disks as maximum

And as I said there is no problem for 1.2 TB disks but for 1.8 TB disks .. there is this funny problem

Beside all these, Dynamic pools are not supported on Hybrid Unity, It is just supported on All flash modes which is totally a shame. HPE supports dynamic pools in 2040, A 5 year old model but Unity hybrid does not support it.

Rainer_EMC · Answer

dynamic pools are only for flash drives - he is using SAS

kelleg · Answer

Did you ever get any response from support? glen

Unity

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