Disk groups on V-max

Hi Srichev,

To try and answer these briefly:

1. If SMC cannot do this (it was a "coming soon to a Symmetrix near you" enhancement request ) then you need to contact your local EMC Support Representative. The bin file will need to be changed to split the FC drives into more suitable disk_groups. This change is online safe with absolutely no impact to data.

2. I am not quite sure about the reference to "stripe thin device and concatenate data devices"? Are you referring to the "Virtual Provisioning Implementation and Best Practices" Technical Note? My understanding is that the recommendation for Thin concatenated meta devices aids oversubscription with a host based data copy. That is, you can create smaller thin devices (to avoid unallocated space on any single Thin volume) and then create and or easily expand these concatenated meta volumes to meet your needs (i.e., just online add meta members without impacting the existing data). The Thin meta's are created on the front end - this doesn't affect the layout of the Thin pool on the back end.

3. The default behavior in the SymmWin program is NOT to allow meta member to use the same physical disk. The SYMCLI command form meta with count= option will obey this default. However if you use the add dev option instead then SymmWin will simply do as you ask and add the specific member(s) to the specified meta (these may be on the same physical disk if you are not careful ). This has been discussed before and I am sure you will find some very good posting on this last topic...

Best Regards,

Michael.

When you create thin device it is already stripped in a pool. Now in the meta from thin device is  preferable concated because you have striping ( one level) .

so you can take advantage of concated meta ( easily expansion)

Boom,I could not locate the doc specifying 64GB limitation.If you can share the link for the doc would be great.

Also,I was going through the Best practices for thin provisioning.This goes back to my/Boom's original question(in other posting).

Thin provisioning uses data devices from pools(logical hypers).If there is a thin device of 64GB(any size,higher than device extent),how to ensure they do not wrap on the same disk..This doc explains how the next device has been picked up in a round robin fashion but not from the disk point of view.

Dis you see the algorithm fro this uses a different disk when a new extent picked up in addition to the new hyper?

Yet for high i/o workload striping meta members is still recommended.

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Wide striping brings up interesting point.Is there any limitation on the thin size(like regular device maxi size is 240GB)?Is that the reason for meta?

Can the meta spread across multiple disk groups and striped instead of concatenation?If this is no,then i understand why concatenation is done?

let me also download the white papers and refer this..

It's not 240G ?

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That recommendation may change in the future, but for today, there is still some performance differences between striped and concatenated.  These are spelled out in the tech note on VP.

Any device, even thin, can be up to 240GB on V-Max.