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Why my tapes don't exceed native capacity?

avv

Active Newcomer
#1
Hi,

tsm 7.1 both clients and server on linux/x64.

All my lto5 tapes do not exceed 1,5 TB of estimated capacity.
I have checked all tapes that are Full and at least 99,5 % occupied
and without reclaimable space. None of then exceeds 1,5 TB.

I have also checked my lto5 drives with ITDT/tapeutil -> compression is enabled.

Device class is defined as follows:

Device Class Name: LTO5C
Device Access Strategy: Sequential
Storage Pool Count: 8
Device Type: LTO
Format: ULTRIUM5C

I have checked my 2 largest B/A clients and there in no "compression" setting in dsm.sys.
AFAIK, default is NO.

I have also checked actual files -> mostly not compressed.

Any hints?

Thanks in advance.
 

RecoveryOne

ADSM.ORG Senior Member
#2
I find LTO compression to be hit or miss in my environment. My copy storage pool generally ends up using 2.4TB to 2.6TB on my LTO6 volumes (Native 2.5TB) volumes 100% full. sometimes I'll get a tape that says its at 2.8TB and 100% full. Long and short of it is it really depends on the data you are sending to the drive. If for example you are sending a lot of tar.gz or mp3, or jpg's or compressed sql backups, and well...any other type of compressed file (outside of TSM compression) the tape drive can't compress it further and in fact could actually inflate it.

As to TSM compression if you are backing up a legacy disk based storage pool to tape, TSM decompresses the data and then shoves it down the pipe to the tape drive. The only pool that doesn't do that (as far as I know) is the new container pools. Client side compression adds some extra processing time to compress the data before its sent to the TSM server. The goal of this is two fold. Reduce network utilization of the client, and reduce space used in your legacy disk based storage pool. And again, some files could grow while undergoing the TSM compression routine.
 

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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).

    Votes: 8 21.6%
  • Keep using TSM for Spectrum Protect.

    Votes: 19 51.4%
  • Let's be formal and just say Spectrum Protect

    Votes: 6 16.2%
  • Other (please comement)

    Votes: 4 10.8%

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