topic Re: EVA 8000 in Disk Enclosures

EVA 8000

phillj_1 — Thu, 29 Jan 2009 10:49:57 GMT

Hi,

we have an EVA 8000. we have added some extra disks to the shelfs. Is the best practice to add the disks to an existing Disk group or create a new one.

If i add the new disks to a disk group it will also start leveling. If if were to create a new disk group would the EVA still need to level the data or would it be fster to just create a new disk group?

TIA

Re: EVA 8000

phillj_1 — Thu, 29 Jan 2009 10:56:56 GMT

oh & one last question.. nothing happens to the existing data if you add new disks to disk groups does it? stupid question but new to EVA 8000.

Re: EVA 8000

Víctor Cespón — Thu, 29 Jan 2009 11:02:36 GMT

1) You need at least 8 disks to create a new disk group
2) Two disk groups gives you more security but less space available and speed.
3) If you add disks to a existing group, there will be a leveling process, but it would not have a visible impact on performance, it's done with very low priority.
4) The data is redistributed among the disks on the disk group, but it's not altered, just moved from one disk to another.

Re: EVA 8000

phillj_1 — Thu, 29 Jan 2009 11:04:36 GMT

thanks for the respone. would it be better to create new disk group? We have added 8 new disk. the existing DC is 24 disks but they are more or less all the same spec disks.

thanks

Re: EVA 8000

IBaltay — Thu, 29 Jan 2009 11:15:24 GMT

Hi,
no the golden EVA rule is the more disks in the disk group, the more spindles/performance in the VDISKs...

here are the best practices:
a) this is for eva 3k/5k because the one for the 4k/6k/8k is unavailable at the moment but the main ideas have remained the same:
http://h71028.www7.hp.com/ERC/downloads/4AA1-5215ENW.pdf?jumpid=reg_R1002_USEN

b) this is for eva 4k/6k/8k availability best practice doc:
http://h71028.www7.hp.com/ERC/downloads/4AA1-4202ENW.pdf?jumpid=reg_R1002_USEN

Re: EVA 8000

Víctor Cespón — Thu, 29 Jan 2009 11:19:03 GMT

The definition of what's the best option depends on your priorities. Better check this document:

ftp://ftp.compaq.com/pub/products/storageworks/whitepapers/5982-9140EN.pdf

Re: EVA 8000

phillj_1 — Thu, 29 Jan 2009 12:05:33 GMT

if you do have differennt size disks e.g 200gb FC, 250gb FC & you add 450gb disks to the Disk Group will this be ok? will any of the space be wasted? All disks are Fibre channel & same speed.

Re: EVA 8000

IBaltay — Thu, 29 Jan 2009 12:38:49 GMT

it is allowed but not recommended from the perf point of view, its better to start the new DG and then grow it...

Re: EVA 8000

phillj_1 — Thu, 29 Jan 2009 12:53:13 GMT

so if the disks were in the process of being added to the DG, the best thing to do would be to wait intil it has levelled & then ungroup each disk from the existing DG?

After this create a new disk group & add the 8 disks?

Thanks