Skip to main content

Viewing Linux partition headers of existing disks


After a boot disk crash, I wanted to make sure existing data disks were unaffected. We use Oracle ASM for all our bare metal database servers and in this case there wasn't a proper backup of the (development) database. ASM marks its disks as being part of an ASM disk group and checking the first block of a partition. This lets you verify that the data still exists.
Upon reinstallation of the OS and ASM software, you can then reuse existing ASM disks and groups and restore the data.

To verify the disks are still marked as ASM disk groups, check the first block of the partition:
dd count=1 if=/dev/sdc1 | od -c
sdc being our first data disk after local disks (sda) and the boot LUN (sdb). Note the text string on the third line in capital letters and the string " D G _ D A T A 1", naming the disk group. You can check the list of available partitions using 'cat /proc/parititons|less'.
Labels:

Comments

Anonymous said…
Or, you could run blkid.

/dev/sdh2: LABEL="LOADVOL1" TYPE="oracleasm"
/dev/sdf3: LABEL="LOADVOL2" TYPE="oracleasm"
August 8, 2008 at 7:26:00 PM GMT+2
Post a Comment

Popular posts from this blog

Tuning the nscd name cache daemon

I've been playing a bit with the nscd now and want to share some tips related to tuning the nscd.conf file. To see how the DNS cache is doing, use nscd -g. nscd configuration: 0 server debug level 26m 57s server runtime 5 current number of threads 32 maximum number of threads 0 number of times clients had to wait yes paranoia mode enabled 3600 restart internal passwd cache: no cache is enabled [other zero output removed] group cache: no cache is enabled [other zero output removed] hosts cache: yes cache is enabled yes cache is persistent yes cache is shared 211 suggested size <==== 216064 total data pool size 1144 used data pool size 3600 seconds time to live for positive entries <==== 20 seconds time to live for negative entries
2 comments
Read more

Preventing PuTTY timeouts

Just found a great tip to prevent timeouts of PuTTY sessions. I'm fine with timeouts by the host, but in our case the firewall kills sessions after 30 minutes of inactivity... When using PuTTY to ssh to your Linux/Unix servers, be sure to use the feature to send NULL packets to prevent a timeout. I've set it to once every 900 seconds, i.e. 15 minutes... See screenshot on the right.
1 comment
Read more

Setting up SR-IOV in RHEL6 on PowerEdge servers

Dell Community : "RHEL 6 provides SR-IOV functionality on supported hardware which provides near native performance for virtualized guests. Single-Root I/O Virtualization (SR-IOV) specification, introduced by PCI-SIG details how a single PCIe device can be shared between various virtualization guests. Devices capable of SR-IOV functionality support multiple virtual functions on top of the physical function. Virtual Function is enabled in hardware as a light weight PCIe function. Operating System cannot discover this function as it does not respond to the PCI bus scan and requires support in the host’s driver. As in PCIe pass-through, a Virtual function of a SR-IOV capable card can be directly assigned to the guest operating system. A virtual function driver running in the guest manages this device."
3 comments
Read more