RE Summary: Running out of space when backing up the OS to a DDS2 tape

From: Spurgeon, John P <>
Date: Wed Apr 10 2002 - 11:51:41 EDT
A friend of mine is fond of saying, "It's best to eat crow while it's

>> Thanks for all the feedback. Everyone seemed to be in agreement
>> that I was running out of space on the DDS2 tape. As to why the
>> backup worked on a previous build with the same physical disks in a RAID
>> 1 mirror, no one could explain precisely what was happening. We all
>> waved our hands and blamed in on the data not compressing as well, which
>> is probably the case. (The computer scientist in me still wishes I could
>> put may hands on the actual compression algorithm.)

Of course, if I was a "real" engineer I would have checked twice to make
the power was plugged in. It turns out that our previous build was NOT using
the whole physical disk in the RAID 1 mirror. The two 8.6 GB hard drives in
the RAID pack had been split into two system drives. One was about 7.5 GB
and the other was about 1 GB (for /tmp). I don't know how I overlooked this
but it explains why we were able to backup system drive 0 to a 120 meter
tape on the old build. Nothing magical about the compression algorithm!

>> I don't even have to modify the RAID layout. Instead, during
>> the Solaris installation, I opt to "Customize the fdisk Partitions". I
>> somewhat arbitrarily selected 1024 cylinders (it's a pretty number)
>> which works out to about 8024 MB for slice 2...

>> Problem solved!

Unfortunately, not quite. We were able to back up drive 0 after reducing the
size of the partition. However, we had trouble restoring the back up. You
Obviously can't use fdisk -B to partition the drive on the server you are
restoring the backup to, because you're right back where you started with
a drive that's too big. So I've decided to change the RAID layout and make
drive 0 about 7.5 GB. I'll mount /var/tmp on the drive that contains the
over space.

John Spurgeon
sunmanagers mailing list
Received on Wed Apr 10 11:58:03 2002

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