[Veritas-bu] Streaming and large data sets
2004-03-19 12:27:43
Subject: |
[Veritas-bu] Streaming and large data sets |
From: |
justin.lloyd AT mci DOT com (Justin C. Lloyd) |
Date: |
Fri, 19 Mar 2004 12:27:43 -0500 |
Ok, maybe I'm missing something.
One recommendation regarding streaming is not to have multiple streams
off the same physical device. By physical device, I am also taking that
to mean a RAID device that spans multiple disks and/or disk arrays. In
my case I have four arrays partitioned into 11 LUNs each and then my
filesystem is built on a volume striped across all 44 LUNs.
So, I have a 400 GB (for now, but growing) data set on that filesystem.
My library's 8 AIT-3 tape drives can write at up to 40 GB/h each.
Therefore if I were to have a single stream the data set would take 10
hours to back up. But if I want it to complete in, say, 2 hours, I'd
have to use 4 drives and hence define 4 roughly equal size streams
(which is what I currently do), which I occasionally have to rebalance
as the data set grows. But this streaming goes against the above
recommendation.
It's possible this really isn't a problem if it just boils down to the
drawback of the streaming taking more time due to additional head
movement. Breaking up a huge stream more than compensates for that
overhead.
Any comments or suggestions?
Justin
--
Justin C. Lloyd
Unix System Administrator
MCI System Technology Solutions
Office 703.886.3219 Vnet 806.3219
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