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Compression and dedup

StiffBoard

ADSM.ORG Senior Member
#1
Hi, if I'm using COMPRESSION Yes (FORCE) ON in my client option set, will compression always be on even if I use COMPRESSION NO in dsm.opt? Nodes have the setting COMPRESSION CLIENT

I'm getting a lot of Object increased in size during compression... and then Sending of object failed on backup clients. Not sure how to go about that...

What is the recommendation for dedup and compression, one or the other or can they work together in a good way? Any general guidelines here?
 

marclant

ADSM.ORG Moderator
#2
Hi, if I'm using COMPRESSION Yes (FORCE) ON in my client option set, will compression always be on even if I use COMPRESSION NO in dsm.opt?
Yes.
What is the recommendation for dedup and compression, one or the other or can they work together in a good way? Any general guidelines here?
If using client-side dedup, you can use client-side compression without issues. If you are still getting data grows, you can use COMPRESSALWAYS NO

If not using client-side dedup, don't use client-side compression because the server will not find duplicates in compressed data. Send the data uncompressed and the server will compress it after it's deduplicated.

(Q10) Which TSM features and options are incompatible or not supported with deduplication?

  1. Client-side encryption is incompatible with TSM deduplication. However TSM deduplication can be used together with SSL (encryption of data in flight) or encryption by the storage device.
  2. LAN-free backup
  3. Simultaneous write
  4. Subfile backup
  5. Client side compression should not be used with server-side deduplication (since compressed objects do not deduplicate well). However, client-side compression used in conjunction with client-side deduplication can provide an effective means to further reduce storage pool data.
source: https://www.ibm.com/developerworks/...Tivoli Storage Manager/page/Deduplication FAQ
 

StiffBoard

ADSM.ORG Senior Member
#3
Hi, thanks for the answer. So, if my nodes have the setting Deduplication Serveronly I shouldn't be using Compression? Even if I do, dedup of bit patterns will still be able to dedup some data?

If I remove the Force flag on Compression Yes in clientoptset, will COMPRESSION NO i dsm.opt work then?

Will COMPRESSALWAYS NO in dsm.opt skip compression even if Force flag is on?

Will check that Dedup FAQ, haven't found that one before, thanks.
 

marclant

ADSM.ORG Moderator
#4
Hi, thanks for the answer. So, if my nodes have the setting Deduplication Serveronly I shouldn't be using Compression?
Exactly.
Even if I do, dedup of bit patterns will still be able to dedup some data?
Not with server-side dedup, but yes will client-side dedup.
If I remove the Force flag on Compression Yes in clientoptset, will COMPRESSION NO i dsm.opt work then?
Correct. Or if you are not doing client-side dedup anywhere, I'd change the client option to COMPRESS NO, to make sure no clients that are doing server-side dedup can use compression.
 

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The Spectrum Protect TLA (Three-Letter Acronym): ISP or something else?

  • Every product needs a TLA, Let's call it ISP (IBM Spectrum Protect).

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