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Data Migration

kodaali
Level 3

Hello,

In our environment we are consolidating storage into fewer arrays replacing the older ones.  As usual, we are adding a mirror to the existing file system using new array luns and removing the older ones. And the i'm not happy with the IO performance and ofcourse, nothing much can be done with that. However, I have observed some file systems usage is very less (some even less than 50%). I am thinking of shrinking the file system and then add plex to it, so that resync will be faster and later I can grow the file system. Though, I do not forsee any issues with this approach as long as file system has enough space for the applications, I would like to take suggestions from others.

 

Thanks in Advance.

Nagesh. 

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Gaurav_S
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If you are using vxfs, then yes, shrinking filesystem should not be an issue & yes the approach is good for a faster plan however I see one issue here, are you strict towards the layout of volumes you are using ?

for e.g lets say your volume is mirrored vol ... now you have shrink it by 50% & then added new plex to it from new Luns, & lets say this new plex has to be mirrored again .. I am wondering about the contigous space allocation ... it shoudn't happen that you have used the contigous space & finally when you have to grow the filesystem , you land up in some restrictions to change the volume layout ..

Hope I am clear ..

 

G

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Gaurav_S
Moderator
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If you are using vxfs, then yes, shrinking filesystem should not be an issue & yes the approach is good for a faster plan however I see one issue here, are you strict towards the layout of volumes you are using ?

for e.g lets say your volume is mirrored vol ... now you have shrink it by 50% & then added new plex to it from new Luns, & lets say this new plex has to be mirrored again .. I am wondering about the contigous space allocation ... it shoudn't happen that you have used the contigous space & finally when you have to grow the filesystem , you land up in some restrictions to change the volume layout ..

Hope I am clear ..

 

G

kodaali
Level 3

Thanks Gaurav. I made a note on mirrored volumes shrinking. We always depend on hardware raid mirror (storage level) and we use only concatenation at software level.

Thanks again, Nagesh.

Gaurav_S
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Thats good then , same thing goes for any other layout as well like striping or layered volumes ... if it is concatenated then shouldn't be a reason to worry..

 

G

Marianne
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You did not mention your VxVM version?

SmartMove was introduced with 5.0MP3. Extract from 5.0MP3 for Solaris:

SmartMove™ feature
SmartMove reduces the time and I/O required to attach or reattach a plex to an existing VxVM volume, in the specific case where a VxVM volume has a VxFS file system mounted on it. The SmartMove feature uses the VxFS information to detect free extents and avoid copying them.

SmartMove provides the following benefits:
■ Less I/O is sent through the host, through the storage network and to the disks/LUNs
■ Faster plex creation, resulting in faster array migrations
■ Ability to migrate from a traditional LUN to a thinly provisioned LUN, removing unused space in the process
In this release, the feature is turned off by default. To turn on and use the full functionality the SmartMove feature, see the following URL: http://www.symantec.com/docs/TECH61880

To use the SmartMove feature, VxVM and VxFS must be version 5.0 MP3 or later.

kodaali
Level 3

Its 4.1 mp2 rp3. :( However, its good to know the new feature(atleast to me). Definitely, I will be using this feature wherever possible. Thank you.

Today I tried shrinking 300g filesystem (3 concat subdisks) by 50% and it took good amount of time(15-20 mins) running fsadm in the background. Does the shrinking always need time? This is the first time I did shrinking. Compared to growth, shrink seems to be a bit slow.

Thanks again.

Nagesh