Maximum number of Hypers can be created in a given disk group .

AFAIK there is a maximum number of hypers you can create in the whole array. there is a limit of hypers you can create on each drive, as well. No known limits in a given disk_group

Let me clarify my question ..

I want create some hypers , say 300 hypers in disk_group , say 2 in a symm .

So preview this " create dev count=300 , size=18414,config=Raid-5,
emulation=FBA,disk_group=2,data_member_count=3; " .

It failed with error " Could not find disks that satisfy our mirror/RAID policy " .

In this case if i want to find out the maximum hypers i can create , i have to decrease( 200 , 150, 100 ) the count and check the script again and again.

Is there any specific way to know the maximum hypers we can create without these trials ?

You can guess more or less how many hypers you can create with a polite guess

First collect freespace informations via symdisk. You need to gather details on every disk in disk_group. You need to know how many cyls are available on any disk. And you also need to account for gaps .. (symdisk -v -hypers -gaps -sid XXX -disk_group N list)

Now let's do some math with desired hyper size. You want to create RAID5 3+1 devices. You need 4 slices on 4 different disks (and remember that the code will enforce strict rules to guarrantee your data is always protected, as stated in error you posted). Each slice will be about a third of desired size. You are creating 18414cyls devices thus each slice will be about 6138 cyls. Since each slice wastes some cyls, let's round up to 6160 cyls.

Now let's go back to symdisk output .. Try to find as many patience as you can since now comes the boring part of the task .. Considere all GAPS and find how many slices you can build in every gap. Suppose you have a disk with 2 gaps: 18414cyl gap (you deleted an unprotected BCV) in the middle of your drive and another (bigger) gap at the very end of the drive, 63521 cyls big.

18414 / 6160 = 2.98
63521 / 6180 = 10.27

You can slice 12 slices from this disk .. neat.
Now repeat the task for each and every disk in diskgroup. Sum up results and divide by 4 (since you need 4 slices for every RAID5 3+1 symdev). Ok .. now you have the maximum number of slices you can create out of your disk_group.

Hi Stefano,

Your post was quiet helpful. I use it regularly. Thanks for that. But I have a question and scenario which is not working as expected.

I have a disk group with 48 disks. I need 4GB R1 devices and try to find how many I can create maximum. I calculated the gaps and have 4551 cyls in each 30 disks. There's no gaps available for 18 disks.

Since I need 4GB devs which is about 4400 cycles, I can create 15 R1 devs maximum. No problem with that until now.

Then I tried to find how many R5 (3+1) devices I can create. Evolving out of your method, The slices will be about 1467 cyls which is a third of 4400.

4551 / 1467 = 3,10

So I can have 3 slices from each disk. 90 slices in all. I divide it by 4 and can have 22 devices maximum.

I applied it but I could create 18 devices maximum. After that, it gives the disk RAID policy error.

Do you have any idea where the difference comes from?