EVA Upgrade

[Steven Clementi]

Bala:

Depends on if you have any available space. If you do not have any available space, you will not be able to swap out a drive since your protection level will then be based on the larger sized disk.

If you have sufficient space to cover the new protection level... Single Protection = 600GB, Double would be 1.2TB, then you can fail a drive and replace it and let it level. Repeat process until you have enough space where you can pull out more than 1 drive, then you can do 2 at a time.

If you have no available space, then you will need to drop your protection level temporarily


Steven

[Balakrishna Kotian]

Hi Uwe / Steven,

Sorry for delay in replying. I got another doubt as of on the Disk enclosure. Like we got 2C4D what happens if the backplane fails in one of the enclosure.

In 2 situtation, one 50% of disk slots are filled and second EVA is full with all disk so single slot free. Is there any possiblity of loosing our data in any of the situation mentioned above.

BR

Bala

[Uwe Zessin]

It's not that easy to generally predict when you get data loss, because the EVA uses a pretty complex data allocation mechanism.

The distribution of the data and the ability to withstand the failure of a complete disk drive enclosure can even change over time if you do a few disk group / ungroup operations.

You really need to check the disk group's "RSS disk state".

[Balakrishna Kotian]

Hi Uwe,

How do I check the RSS disk state and find out will the EVA (loss of data) fail if one of my Enclosure fails.

BR
Bala

[Uwe Zessin · Accepted solution]

It's on the disk group properties page (on the right).

none - means that the system cannot tolerate the failure of a disk drive enclosure, but it does not tell where the limitation is

mirror - means the system can tolerate the failure of a disk drive enclosure as long as you only use VRAID-1 virtual disks

parity - means the system can tolerate the failure of a disk drive enclosure for VRAID-1 or VRAID-5 virtual disks


Note that this is a per disk group characteristic - another group that shares the same disk drive enclosures can have a different state!!

[Balakrishna Kotian]

Hi Uwe,

Thank you very much for all your replies. Do you have any document on this stating when RSS is set to mirror with mix of Vdisk 1 & 5 then single enclosure failure will loose the EVA.
Even though all the slots are filled in the EVA still cannot survive.

Can I change it to parity without disturbing the disk group or we need to redo everything from scratch.

Bala

[Uwe Zessin]

Hello Bala,

I've checked a few documents, but I didn't find a description - it might be hidden in Command View EVA's online help, though.

It does not matter if all slots are filled or not - it really depends on how the data is layed out over all enclosures. Now, you wrote that you have an EVA3000. That model supports a maximum of 4 disk drive enclosures, so you will *never* be able to bring a disk group into 'parity' state, sorry.

For the EVA6000, you would need 8 enclosures, make sure that disk groups are multiple of 8 disks and even then you might get into a situation that 'parity' is not possible.

[Peter Mattei]

Hi Bala

Instead of messing around with upgrading to EVA5k or 6k, why dont you just add another EVA to your environment. This can be done concurrently, will increase the overall performance, does not take much time and you will not put your data on risk!

Cheers
Peter

[Balakrishna Kotian]

Hi Peter,

I had two questions in mind one was upgrade for which I got the answer and second was failure of one enclosure in eva 3000 will bring down my SAN? Because if there is failure and we need to have more then 4 enclosure then we can plan for upgrade of controller or else plan for upgrading disk in the EVA.
As per Mr. Uwe he mentioned in RSS if disk group contains both Vdisk 1 & 5 and set to mirror will cause a failure. If thats the case then my DG is set to mirror so wanted to confirm if its anywhere documented. Once I have that then we can come in to some conclusion which path is required to increase the capacity with complete redundancy.

BR
Bala

[Peter Mattei]

Bala

First you have to understand that the EVA is a midrange array and is designed without SPOF (Single Point of Failure)
This is achieved by having
- 2 Controller
- RAID protection
- Disk enclosures with 2 IO modules and seperate FC loops
- two independend power supplies per enclosure

The loss of an enclosure is not considered a single failure, because it needs more than one component to fail. This could be
- 2 power supplies in an enclosure
- 2 IO modules in an enclosure
- both FC loops in an enclosure

If you want to read more about EVA design considerations like RSS see
http://h20000.www2.hp.com/bc/docs/support/SupportManual/lpg29448/lpg29448.pdf

Cheers
Peter