EVA5000 best disk distribution

[WilliamSmith11]

Hi

My case is as follow

A customer have an EVA5000 , he bought new disk drive of 300GB (15 disk to exact).
At this moments he have two disk groups .

The system have a total of 106 disk (106 disk of 146GB)

He is planning to add all the new disk drive to the primary disk group.

My question is

Whitch will be the best practice to the distribution of the new disk drive ,fill vertically , from the the shelft one to the last on and start again in the shelf one .

the storage is a 2c12D.

Thank you .

W.S

P.S. This thread has been moevd from Disk to Storage Area Networks (SAN) . - Hp Forum moderator

[Uwe Zessin · Accepted solution]

Yes, that's the suggested way: fill vertically. If you fill horizontally, you can end up with two mirror members in one disk drive enclosure, for example - not a good thing.

Another best practice is to always add new disk drive enclosures in pairs, by the way. A disk group should always have an even number of disk drives.

You can find a best practice guide on the EVA5000 documentation pages, although it seems a bit outdated.
http://h20000.www2.hp.com/bizsupport/TechSupport/DocumentIndex.jsp?contentType=SupportManual&docIndexId=3124&locale=en_US&prodTypeId=12169&prodSeriesId=321347

[Mike Reznak]

Hi,

also mixing disk sizes isn't the best practice. If I remember it right, there are some issues about leveling and disk utilization in this case.

Mike

[Luk Vandenbussche]

Hi WS

I just want to add that is advisable to create an extra diskgroup.

[Uwe Zessin]

Yes, you remember right, Mike. A larger disk drive will store the same percentual (sp?) amount of data. E.g. your disk group is 50% full, a 146 GB disk drive will hold about 73GB, but a 300GB disk drive will hold about 150GB.

Another thing is that the amount of space reserved for distributed sparing is calculated from the largest disk drive in the disk group.

Assuming a protection level of 1/single - the disk group reserves about 2*146GB - you are 'loosing' 2x 146GB disk drives. If you put a single disk drive of 300GB into the group - you suddenly loose about 2x300GB (about 4x 146GB disk drives!) for the distributed sparing.

[Ivan Ferreira]

But if you create a new disk group with the new drives, you will also loose capacity because you "should" specify a protection level of at least single for the new disk group. So, if you add the disks to the current disk group, or if you create a new disk group with protection single, you may end up with more or less the same capacity.

[Uwe Zessin]

Assuming protection level=1 and creating a new disk group with the new disk drives you will end up with LESS capacity!

2x146GB from existing group plus 2x300GB from new group will be set aside, versus 2x300GB if you add the new disk drives to an existing group.

[WilliamSmith11]

I forget to tell you that the protection is double so I will have 4x300GB reserved .

[Uwe Zessin]

That's correct - I was using level 1 in order not to scare you too much ;-)

[Sameer_Nirmal]

Hi,

I am not sure how the current 106 disks are installed in the EVA. But usually filling of the disk shelves slots should start from
front left side ( i.e. from Bay 1 ) top to bottom and growing horizontally to the front right. Disks should be installed vertically with intension of using slots across all the shelves. Starting from left has advantage in diagnosing the problem related to disks in a shelf in future.

It is always better the array should contain multiple of 8 disks or total number of disks
should be divisible by 8. Moreover the disk groups should contain multiple of 8 disks.

You may need to look at the survival in case of a disk shelf failure in your 2C12D EVA or rather maintaining it after adding the new disks.