thin LUN expansion

[Srinivas Adusumalli]

Hello guys,

 

 

Any one of you come across thin LUN expansion in VMAX ?

 

Regards

Srini

[Vidhyadhar Vanam]

Hello annaya,

Most probably, thin lun should have been concatenated.If so, it is just equivalent to adding a meta member to a LUN.

add dev xxxx:xxxx to meta <orig LUN>; ( provided existing thin lun should be a meta lun )

If it is striped by any chance, then we can still add a meta member but however, we can never reduce it.

add dev xxxx:xxxx to meta <orig symdev>, protect_data=TRUE, bcv_meta_head=<temp symdev>; ( I have not tried this one in prod )



Regards,
Vidhyadhar.

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[Srinivas Adusumalli]

Thambi,

 

Much appreciated your response. Is this online activity ? Have you done this before ?

 

 

Regards

Srini

On Wed, Jan 9, 2013 at 1:12 PM, Vidhyadhar Vanam <vidhyadh...@gmail.com> wrote:

Hello annaya,

[Santhosh Kumar]

Annaya,

 

Concatinated meta expansion is a straight way procedure, just add the newely created hyper/meta to the original meta. whereas expanding striped meta is bit complicated, where a dummy(bcv) devices should be created and then hypers need to be added to original meta using the dummy device as staging area. this device helps in restriping the data across new hypers after expansion.

 

I had done this in my environment. Attached is the SOP for the striped meta expansion in V-MAX. This can be done online. But if it is a production better practise to take a downtime of 15 mins for 100 GB & a clone copy(optional), as there may be some perf. issues(if original disk size is huge capacity) on device due to data transfers from source to staging device and vice versa during activity.

 

Regards.,

Santhosh.D.

On Wed, Jan 9, 2013 at 1:07 PM, Srinivas Adusumalli <srinivasa....@gmail.com> wrote:

appreciated your response. Is this online activity ? Have you done

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Regards,
Santhosh Kumar.D

[Srinivas Adusumalli]

Iam bit confused with EMC primus. I believe , confused with hyper vs meta ..after Re-reading twice or thirce ..clear now.  Thank you guys !

ID: emc243183
Domain: EMC1
Solution Class: 3.X Compatibility

Goal       Is there a way to expand / grow an existing thin device?

Fact       EMC SW: Solutions Enabler SYMCLI

Fact       EMC SW: Symmetrix Management Console (SMC)

Fact       The EMC Solutions Enabler Array Controls CLI Product Guide

Symptom    Unbinding thin devices from the pool will result in data loss.

Cause      The EMC Solutions Enabler Array Controls CLI Product Guide states the following in the "Configuring thin meta devices" section:  "Only unbound thin devices can be formed into a metadevice." However, unbinding thin devices from the pool will result in data loss. The documentation should read: "Only unmapped thin hypers can be formed into a meta device." The following procedure is evidence that this will work.

Fix        Restrictions:
•    When forming a meta, this is an offline event.  Access to the existing hyper being expanded is forbidden.
•    To preserve the data, concatenation is required.  The protect_data option is NOT supported with thin devices; therefore, forming a stripped meta or expanding a stripped thin meta will destroy data.
•    The existing hyper must be unmapped to form a meta.
•    The new thin hypers you are adding to the meta head (existing production device) cannot be bound to a thin pool.
•    The existing thin device cannot belong to a TimeFinder or SRDF pair.  Sessions must be taken down.
•    You cannot mix thin and data devices.
To form an existing the thin hyper into a meta, perform the following steps:
1.    Unmount the existing thin hyper from the host.
2.    Unmap the existing thin hyper that you wish to grow.  If on a Symmetrix VMAX, you must remove the devices from the storage group first.
3.    Make sure the new hyper(s) being added to the existing thin hyper is unmapped.
4.    Make sure the new hyper(s) being added to the existing thin hyper is unbound.
5.    This step currently cannot be done from SMC.  EMC Engineering is investigating this.  From the command line, form a concatenated meta from the existing thin hyper and add the thin hyper(s) you wish to use for concatenation.  Refer to the example command file below.
6.    Put the thin meta head back in the storage group or map the meta head (pre Symmetrix VMAX).
7.    Rescan the host for devices.
8.    Reconfigure devices under path management control.
9.    Mount the device.
To grow an existing concatenated thin meta, perform the following steps:
1.    Check with your OS, LVM and application providers for best practices on changes to device sizes because some vendor combinations may require reboots or device removal to rescan for the new device size.  An outage is not required by EMC operations but, might be required by the host software configuration.
2.    Make sure the new hyper(s) being added to the existing thin hyper is unmapped.
3.    Make sure the new hyper(s) being added to the existing thin hyper is unbound.
4.    If already a meta, just add the additional hyper(s) with the "add dev" option.
5.    Rescan the host for devices.
6.    Reconfigure devices under path management control (If required).
7.    Mount the device (If required).


Note       Understanding the terminology is crucial to understanding this solution. 
•    Hyper - A single logical number on a Symmetrix that represents a disk to the host.  This can be part of a meta but, never a meta.
•    Meta - A logical grouping of hypers to make up one device.
•    Device - A single logical number on a Symmetrix that can be either a hyper or a meta.  This word can be misleading as it is frequently used interchangeably between meta and hyper.


Note       Example command file for forming a meta:
form meta from dev 0010, config=concatenated;
add dev 0013:0014 to meta 0010;

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