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Disk groups on V-max

I have this new V-max and testing it....V-max with two drive types EFD and FC 15k drives.

By default,if you look at the V-max it creates two disk group types by drive type.

Planning to split FC drives into two RAID types RAID1 and RAID 5.V-max allows to creates both the RAID type on the same physical disk.

-Is there any way to configure more than one disk groups from the FC drives(could not locate an option in SMC).Can this be done on Bin file level?

-When using the Thin Provisioning,EMC recommendation was to use  Strip Thin device and concatenate data devices.I am not clear on that..does that mean create a Thin device x times as original data device and stripe it..then future additions would be only on the back end?am i thinking right about this?

-Meta devices:While creating meta devices,is there any way ensure the hyper do not wrap up on the same disk?Is there any auto meta creation on V-max?

Sharing your experiences would be appreciated.

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8 Krypton

Re: 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.

8 Krypton

Re: Disk groups on V-max

On the point 2,Thin provisioning,thought the other way.Creating thin devices and stripe it but on the backend data devs concatenate it. or am i thinking some thing weird.
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Re: Disk groups on V-max

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)

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8 Krypton

Re: Disk groups on V-max

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

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Re: Disk groups on V-max

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.

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Re: Disk groups on V-max

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..

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Re: Disk groups on V-max

Maximum size is 64 GB for thin device.
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Re: Disk groups on V-max

It's not 240G ?

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Re: Disk groups on V-max

Up to my knowledge max size is 64 gb, thin extent size is 768kb for raid-1. (according to emc it may be change in feature)