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Re: EVA Disk Protection Level.

 
Munees
New Member

EVA Disk Protection Level.

Hi Champs!

I have a disk group with 24 disks with single protection level in EVA. which means 2 out of 24 will be set as spare drives. My question is whether any 2 physical disks will be dedicated as spare drive or it virtually takes space from each disks?

Thanks in advance..

Cheers,
Munees
10 REPLIES 10
Patrick Terlisten
Honored Contributor

Re: EVA Disk Protection Level.

Hello,

the space is reserved over all disks in the disk group, there are no dedicated spare disks in an EVA. The space is reserved for rebuild, but as long as there is free space in the diskgroup, the EVA will use free space in the DG for rebuild.

Regards,
Patrick
Best regards,
Patrick
Sivaramakrishna_1
Honored Contributor

Re: EVA Disk Protection Level.

Hi,

Actually 2 Disk means, not Disks. It will spare the 2*Max Size HDD space on the storage.

Suppose if u have a mixture of 146 and 300 and 450 in a single DG, it will reserve the 2*450GB Size on the DG.
Munees
New Member

Re: EVA Disk Protection Level.

Hi,

Thanks for your replies.

I got another qustion now. If the DG consists of mixture size of disks, how the space managed for disk protection? Is it eqally allocated from each disk or depends on disk size?
Johan Guldmyr
Honored Contributor

Re: EVA Disk Protection Level.

If you have a mixture of disk sizes in a disk group, for single disk protection it reserve 2x size of the largest disk.
Víctor Cespón
Honored Contributor

Re: EVA Disk Protection Level.

The "disk drive failure protection" option is only to set a soft barrier so you can be sure to have enough free space on the disk group to be able to rebuild all RAIDs.

The reconstructing process uses the free space on all the disks to rebuild the RAIDs. If you set the option to None and you have the space equivalent to 2 disks free, you're on the same situation as setting the paramenter as Single.
Suhag
Occasional Advisor

Re: EVA Disk Protection Level.

I gone through the entire post and also found very usefull information. I want to post my scenario here as we are facing the problem releted to Disk protection level.

 

We are using EVA6400. We have created single disk group consisting of 17 no. of 1 TB disk . I have created some LUN/vDisk  with RAID1 and some with RAID5 and disk protection level was single.

 

Due to some issue,  2 no of disks from the same array were failed and all the vDisk/LUN were showing red cross and eventually it was a big disaster and all the data were lost permenentely.

 

To overcome this issue in future, i have created disk group once again and this time i set the  Disk protection level to double. What i was thinking that by doing double disk protection, i can sustain (or save data)  up to the failure of two disk.

 

Is my thinking is right? that by doing double disk protection, i am going to save data in case of 2 no of HDD fail simulteneously.

 

Please explain

 

 

Thanks in Advance,

Suhag Desai

TCS

hvhari
Esteemed Contributor

Re: EVA Disk Protection Level.

Double protection level will ensure enough space is available for re-construction of data and ensure redundancy upto two disks failure without needing a physical replacement. But the failures can not be simultaneous, as it is depnding on the parity. (when the failed disks are from different RSS Sets in eva, then you have the chance of not losing the data, even if both failed at same time.)

Regards,
Hari

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Uwe Zessin
Honored Contributor

Re: EVA Disk Protection Level.

The so-called "protection level"

 

     DOES NOT !!

 

protect any data. It is only a space reservation.

 

An RSS (redundant storage set)

 

     DOES NOT !!

 

protect any data. It is used to limit the size of a failure domain.

 

The only data protection is in the virtual disk's VRAID-level (1,5,6).

 

Create a virtual disk in VRAID-0 and no amount of "protection level" or "RSS" can prevent data loss from the failure of a single disk drive!!!

 

.
sumitds074
New Member

Re: EVA Disk Protection Level.

Hi,

Can any1 tell me wat is the meaning of protection level?
Some say it increases the number of drives count when we increase the protection level. But some say it only increases space in a disk
Can any1 pls tell wat is the functionality of this in a simpler way?
Thanks,
Sumit