roysubs
1 Copper

Migrate a symdev/meta within a single VMAX non-distruptively?

There are many methods to migrate devices to new arrays, but what are all of the methods are available to us to migrate a device (thick or thin) to a new device (thick or thin) within a VMAX?

Say that I have a device 8E1 (could be a single symdev or a meta-head) and then create another device (or meta) 8F6 that is either a single symdev or meta that is the same size of larger than 8E1.

- What possible methods (any/all methods would be appreciated) would we have to migrate 8E1 to 8F6 in this case?

- Also, in terms of presenting that device to the existing host, are there means to do that non-disruptively?

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12 Replies
AranH1
4 Beryllium

Re: Migrate a symdev/meta within a single VMAX non-distruptively?


To migrate to an existing device would only be timefinder/clone within the array.

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AranH1
4 Beryllium

Re: Migrate a symdev/meta within a single VMAX non-distruptively?

The above comment is for thin devices and thick>thin migrations.

I should add that with thick to thick migrations you can use symmigrate to migrate to an exising thick device.

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rwise1
1 Copper

Re: Migrate a symdev/meta within a single VMAX non-distruptively?

So symmigrate can migrate thick to thick, but not thin to thin. Seems quite an oversight that, but ok thanks.

- Can symmigrate migrate data non-disruptively online to the host?

- Do I need a particular license to use symmigrate?

- I read here that PPME with TimeFinder Clones is a good method https://community.emc.com/thread/145129

(requiring the paid for Clone licese, and also the PPME-SymClone license, though apparently that is free).

- Are there any other methods might be open to us to migrate devices (specifically within an array, as surely this facility should be quite simple for the array to perform)?

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AranH1
4 Beryllium

Re: Migrate a symdev/meta within a single VMAX non-distruptively?

Symmigrate can indeed migrate a thin device from one thin pool to another. That was not the question. The question was what can be used to migrate to a new device. If you just want to migrate a thin device to a different pool then symmigrate is designed for that process.

It is a non-disruptive processs and can be used in a tiered environment to even move extents from only one specific pool to another target pool without rebinding the thin device to the target pool. Very handy. The license is included in your enginuity license I believe.

When using thick devices (disk based provisioning) you can use symmigrate to migrate to configured (existing device) or unconfigured space (free space).


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rwise1
1 Copper

Re: Migrate a symdev/meta within a single VMAX non-distruptively?

Sorry, I see that you in fact said that it *cannot* do thick to thin, so it can only do thick to thick (that it can be used to migrate a thin device from one pool to another is also useful, I will use that). ok, so that's great and if I understand well:

- symmigrate can migrate a thick device to a different thick device of the same size or larger, or to unconfigured space to create a new thick device (both of these operations are non-disruptive and safe to do while online to the host).

- symmigrate *cannot* migrate a thick device to a new thin device (or to unconfigured thin pool space)
- symmigrate *cannot* migrate a thin device to a new thick device (or to unconfigured thick space)

- symmigrate *cannot* migrate a thin device to a new thin device (or to unconfigured space in the pool)

Seems odd that symmigrate cannot migrate a thin device to another thin device: would seem a complimentary function to migrating thick to thick ... But anyway, for migrating thick to thin, or thin to thick or thin to thin, we can only do this by TimeFinder Clones, requiring the TimeFinder Clone paid license.

Seems very confusing that thick to thick migration is base (free) functionality, while thin to thin migration is only possible via a paid for license. If anyone knows of any other possible option to migrate thin to thin non-disruptively (also disruptively would be interesting to know). Do you have a document reference / link for this procedure handy AranH? Thanks.


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M_Salem
3 Argentium

Re: Migrate a symdev/meta within a single VMAX non-distruptively?

Hello rwise,

Welcome to EMC Community.

Symmigrate can migrate thick to thick However, migrate to larger space is not supported with any code.

migration from thick to thin and thin to thick is not supported with symmigrate. You can overcome this by using host based migration tool like PPME.

Symmigrate supports thin to thin migrations.

PPME can be used without TF on the array, You can use PPME hostcopy. It is a free license In order to  check if it you have it, run this command:  powermt check_registration. if capabilities were "All" then your PPME license is included. If only Multipathing is listed there then you will need a separate license for hostcopy, again it is for free PPME hostcopy consumes some of the host resources as you offload the migration completely to the host. PPME with TF offloads this to the array so we have an advantage here over PPME Hostcopy. Both techniques will do the migration online

Hope that helps

Mohammed Salem

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AranH1
4 Beryllium

Re: Migrate a symdev/meta within a single VMAX non-distruptively?

rwise,

You stated:

- symmigrate *cannot* migrate a thin device to a new thin device (or to unconfigured space in the pool)

This is correct but I fail to see this as a limitation. If you need to move a thin device you simply migrate it to another pool. I don't see the value in migrating it to a new device ID.

The functionality exists in thick devices becuase they are limited by their physical location within the disk group and device configuration, and being able to migrate to another thick device allows the thick device to change RAID type. With thin devices if you want to change the RAID type associated to a thin device you just migrate it to a pool of the desired RAID type.

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Highlighted
dynamox
6 Thallium

Re: Migrate a symdev/meta within a single VMAX non-distruptively?

let's be more specific, PPME is not free unless you have an active maintenance contract for the regular PowerPath license. If you are using PowerPath without the license (basic failover, which gives you very limited failover functionality) you will need to purchase PPME license.

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rwise1
1 Copper

Re: Migrate a symdev/meta within a single VMAX non-distruptively?

> This is correct but I fail to see this as a limitation. If you need to move a thin device you simply migrate it to another pool. I don't see the value in migrating it to a new device ID.

I guess a situation that I was thinking of, if not *needed* in anyway whatsoever, would be useful in terms of running a tidy array, was that:

- I create an 8-way meta for an application.

- A month later they need it expanded, in the meantime I have done more allocations

- After 3 or 4 expansions, I end up with a 19-way meta with non-contiguous symdevs spread out a lot.

Again, I *know* that this is not required to do this, but it does occur to me that it would be a nice-to-have option to be able to create 19 contiguous symdevs and then move the data onto this tidy / contiguous meta-device. So do you reckon that this is impossible to do short of using PPME ? I'm still quite surprised if there is not be a way to accomodate this easily to be honest as migrating internally to the array should be really simple (I would have thought).

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