[NTLUG:Discuss] I/O Block Size and Slow Tape Backup

Stuart Johnston saj at thecommune.net
Thu Sep 15 14:59:54 CDT 2005


Recently, we have been updating our servers from a 2.4 based distro to a 
2.6 based version.  We noticed our tape backups would not finish within 
the normal alloted time.  In my testing I found that 2.5G of data would 
take 20m with 2.4 and 5h30m with 2.6.  I tested with a Knoppix CD so 
that I could easily switch kernel versions with everything else staying 
the same.

I finally found that increasing the I/O block size solves the problem. 
I understand that the larger blocks keep the tape streaming and 
therefore faster but why the difference between kernel version?  Does 
2.6 use a smaller default block-size than 2.4?

Thanks,
Stuart Johnston




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