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How to migrate a storage system
holding a couple PBytes of data
into IBM Spectrum Scale (GPFS)
over the weekend
HSM migration
with EasyHSM and Nirvana
Feb 2017 Igor Sfiligoi
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• You have a storage system containing
a couple PBytes of data
• And you want to migrate off of it
– Due to cost, performance, age, etc.
• How long will it take?
– At 10 Gbps – at least 3 weeks
– Longer if you have smaller files
• What will your users do during that period?
– How do you handle consistency?
So, you want to migrate a PByte storage system
2PBytes/10 Gbits/s ~= 1.7M secs
1.7M secs / 3600 / 24 ~= 20 days
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• Moving 2 PBytes of data in one shot
takes a long time
– Not much you can do about it(short of spending a fortune in networking, and even then…)
• But why do you want to do it in the first place?
– User convenience(single namespace)
– Data consistency(which copy is the authoritative)
– Let’s be done with it
But why move all the data at once?
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• Moving 2 PBytes of data in one shot
takes a long time
– Not much you can do about it(short of spending a fortune in networking, and even then…)
• But why do you want to do it in the first place?
– User convenience(single namespace)
– Data consistency(which copy is the authoritative)
– Let’s be done with it
But why move all the data at once?
Don’t need data to be moved,just the file structure
(the namespace, metadata)
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• A PByte-class storage system will likely have
about 100M files in it
• Using a dedicated tool, you can
catalogue them in less than half a day
– General Atomics’ Nirvana has proven
it can crawl 100M files
in 3h when on IBM Spectrum Scale™(GPFS), and
in 6h when on Isilon™
How long will it take to migrate just the metadata?
2PBytes/ 100M files = 20MBytes/file
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• A PByte-class storage system will likely have
about 100M files in it
• Using a dedicated tool, you can
catalogue them in less than half a day
– General Atomics’ Nirvana has proven
it can crawl 100M files
in 3h when on IBM Spectrum Scale™(GPFS), and
in 6h when on Isilon™
How long will it take to migrate just the metadata?
2PBytes/ 100M files = 20MBytes/file
OK, now I know what is
in my old system.
Now what???
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• If you are migrating to an
IBM Spectrum Scale (GPFS) storage resource,
you can use General Atomics’ EasyHSM to create
HSM stubs to the old storage system
• Creating the HSM stubs
can be done fast
– A few hours for 100M files
• Users see all the files
in the new storage immediately
– Data is transparently (reverse) migrated
into GPFS when needed
Using EasyHSM on IBM Spectrum Scale (GPFS)
Storage System to Decommission
EasyHSM +
Nirvana
Also known as recallin HSM terminology
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• The old storage system is scanned once– Direct user access should be prohibited at this point
• HSM stubs are created in target GPFS system– Users can start using the GPFS system
– They should not notice any difference
• When a user reads the content of a file,
data is recalled from old storage system into GPFS – Transparently, through EasyHSM, using
GPFS-native HSM capabilities
• Sysadmins can schedule also explicit recalls– Possibly during low-activity hours
• Once data in GPFS, copy in old storage not needed– EasyHSM provides tool for automatic deletion
In more detail
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• The old storage system is scanned once– Direct user access should be prohibited at this point
• HSM stubs are created in target GPFS system– Users can start using the GPFS system
– They should not notice any difference
• When a user reads the content of a file,
data is recalled from old storage system into GPFS – Transparently, through EasyHSM, using
GPFS-native HSM capabilities
• Sysadmins can schedule also explicit recalls– Possibly during low-activity hours
• Once data in GPFS, copy in old storage not needed– EasyHSM provides tool for automatic deletion
In more detail
Can easily be completed
over a week-end
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• The old storage system is scanned once– Direct user access should be prohibited at this point
• HSM stubs are created in target GPFS system– Users can start using the GPFS system
– They should not notice any difference
• When a user reads the content of a file,
data is recalled from old storage system into GPFS – Transparently, through EasyHSM, using
GPFS-native HSM capabilities
• Sysadmins can schedule also explicit recalls– Possibly during low-activity hours
• Once data in GPFS, copy in old storage not needed– EasyHSM provides tool for automatic deletion
In more detail
Data migration can
span months, without
any major disruption
to business processes
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• Nirvana and EasyHSM are both developed and
maintained by General Atomics
– Nirvana has been around for a long time• See Wikipedia page for more details
https://en.wikipedia.org/wiki/Nirvana_(software)
– EasyHSM has been released in Feb 2017
• Employ a subscription licensing model
– Pay for the period you use them
– Not capacity based
(fixed price, no matter how big is your storage system)
About the products
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• If you want to try it out, fill the request form
on the Nirvana home page:
http://www.ga.com/nirvana
• If you just want to know more, feel free to
– Contact me at
– Contact the program manager at
For more information
