EVA 4400 Protection level and Raid level

[mihaib200]

Hello,

If I have this:

9x146GB and 3x450GB disk on EVA 4400 with 1 controller and 1 disk shelf and 1 disk group.

What is the best config for having the best protection?

- Protection lvl 1, vraid 5?

- Protection lvl none, vraid 6?

In my opinion, if i understood well, protection level it's just a reserved capacity on the disk group meaning that if one disk fail (let's say i have protection lvl 1, so 900 GB reserved on disk group), the information from the failed disk is rebuilt on the other disks to the reserved capacity without changing the disk (supposing EVA is full capacity used). EVA will do this anyway if i have protection level set none and enough free space (2xfailed disk), right?

If i set vRAID 6, it means that i'm safe with 2 PHYSICAL disks failed?

I know this is not a good config, mixing different capacity disks in the same group and loosing alot of space and performance, but in my situation i'll go for Protection lvl to none and vRAID 6. What do yo think? Also, vRAID 6 should be much faster on rebuilding then vRAID 5, but slower on write performance?

How EVA calculate estimated capacity for VRAID 6 given the config above?

 LE: How EVA will make the RSS's? 2 RSS's, 6 physical disks per RSS?

Regards!

[giladzzz]

Hi

Protection level is disk space left for sparing that will not appear in your total capacity.

this capacity is always from the largest disk size that is single protection means you lose 2 disks (2 X450 GB)

of the largest size and double means you loose 4 disks.

raid is the way data is spread on the disks if you have raid 5 you loose 20 % and raid 6 40 %

and you can be sfe if 2 disks fail

RSS is an internal setting that the EVA sets. it tries to group the disks into groups of 8 (1 RSS) if

it can but it can go down to six disks and up to 12 disks. you will probably have 2 RSS.

Regards

if this helps give KUDO

[mihaib200]

After adding some more drives:

- With 6x146 GB and 6x450 GB, protection lvl 1 >> the space available for vRAID 6 reported is: ~ 815 GB

- After ungrouping 1x146 GB, so with 5x146 GB and 6x450GB, protection lvl 1 >> the space available for vRAID 6 "jumped" to: 1.5 TB.

I think this is due to the number of RSS >> with 12 disks, i have 2 RSS (each group with 6 disks) and with 11 disks i have only one RSS.

[mihaib200]

So, with 12 disks on one shelf and one disk group, 2 RSS and vRAID 6, I can loose 2 physical disks from each RSS. A total of 4 failed disks (2 disks from each RSS) if i'm lucky, right?

With only 11 disks I can loose only 2 physical disks because i have only 1 RSS, that's correct?

Regards,

M.