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Wonder if anyone can help with this issue, we running RHL 5 on HP Proliant DL580 G7 it has 2xCPU @1.87GHz 6XCORES each & 64GB RAM. lately backing up a directory (62GB) with tar (tar -czvf filename.tgz /directory/to/backup) is taking up to 3 hours.

The directory being backed up is a LUN connect via iscsi at 1Gb/s NIC. So far i have tested the R/W to that LUN and i am getting 35MB/s to 40MB/s. viewing top tar is hitting 100% processor usage.

although i have my money on processor performance, i would like to hear some of your opnion on this. i need to uderstand why its taking 3-4 hours to complete the tar process.

any ideas?

thanks & regards.

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1  
As you mention top, is there any I/O wait? –  tink Jun 5 '13 at 17:21
    
the closest thing to "wait" i have seen is this "scsi_wq_2" process poping up, still trying to understand what it means. anyone? –  Vladimir Jun 5 '13 at 17:30
    
Tar is rarely a CPU-bound operation. I agree with @tink...check your iowait. –  EEAA Jun 5 '13 at 17:30
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@EEAA -- examine the tar command line CAREFULLY, it has a 'z' option in it. (Hint: being compressed, not just copied.) –  mdpc Jun 5 '13 at 18:17
1  
It's time for a smarter backup solution. –  Michael Hampton Jun 5 '13 at 18:22

1 Answer 1

up vote 4 down vote accepted

You're compressing (gzip, even) 62 GB of data. At 40 MB/s, that transfer would take ~30 minutes on its own. However, gzip involves the CPU greatly. If you're pinning both cores at 100%, then there's your answer.

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This is the answer. Remove the compression and it'll speed right up. –  kormoc Jun 5 '13 at 18:23
    
at the cost of increased destination size. –  mdpc Jun 5 '13 at 18:26
    
Well yes, it'd be the same size as the source (62 GB). –  Nathan C Jun 5 '13 at 18:31
    
gzip was single threaded last I checked. –  3molo Jun 5 '13 at 18:44
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Hi All, i ended up using lbzip2, and gladly its now taking 30 minutes to backup the data. i will accept NATHAN C suggestion as an answer. –  Vladimir Jun 10 '13 at 8:52

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