Skip to main content

Add a mirror with ZPOOL/ZFS

Recently I had a huge debacle involving a USS7110, which happens to be a Sun x4240 with ZFS, moderately over-glorified ;-)

As a result of the disaster I was essentially pulling the mirror disk from my alternate system (uss02) and putting it into my primary system (uss01) to get that system running again. Simple enough... I guess. The problem I ran into, and this will be specific to the USS only, is that the drives in the array are either identified as "system" or "data" (which you can see from the BUI). During my drive swapping, I had pulled the "data" spare, and mirrored the "system" OS disk to it. Somehow it left the data disk-type stamp on it. The drive mirrored fine and all, but when I would go to create a new zpool, the OS drive would appear to be a valid disk to put the data on. I obviously didn't go through with that step, but I can't imagine what would happen if I had.

Chances are you will never be in the position I was in, so the details hardly matter. The crux of this post is how to add a mirror to an existing ZPOOL.

  • You will notice that my "system" zpool only has one disk.
  • I had to use -f because the disk I was about to mirror to had previously belonged to another pool. I suppose you could reformat that drive before going through with this activity, but... the drive has the SATA WWN on the label, so I was certain I had the correct device
  • Why am I posting something so trivial/simple... the syntax seemed odd to me and therefore I wanted a reference to successfully pulling this off. See the very bottom for an explanation.
uss02# zpool status
pool: system
state: ONLINE
status: The pool is formatted using an older on-disk format. The pool can
still be used, but some features are unavailable.
action: Upgrade the pool using 'zpool upgrade'. Once this is done, the
pool will no longer be accessible on older software versions.
scrub: none requested
config:

NAME STATE READ WRITE CKSUM
system ONLINE 0 0 0
c0t5000CCA0002CE1C4d0s0 ONLINE 0 0 0

errors: No known data errors

uss02# zpool attach -f system c0t5000CCA0002CE1C4d0s0 c0t5000CCA0002D2844d0s0
uss02# zpool status system
pool: system
state: ONLINE
status: One or more devices is currently being resilvered. The pool will
continue to function, possibly in a degraded state.
action: Wait for the resilver to complete.
scrub: resilver in progress for 0h0m, 0.02% done, 8h10m to go
config:

NAME STATE READ WRITE CKSUM
system ONLINE 0 0 0
mirror-0 ONLINE 0 0 0
c0t5000CCA0002CE1C4d0s0 ONLINE 0 0 0
c0t5000CCA000D2844d0s0 ONLINE 0 0 0 7.07M resilvered

errors: No known data errors


Explanation:
zpool attach [-f] pool device new_device

Attaches new_device to an existing zpool device. The
existing device cannot be part of a raidz configuration.
If device is not currently part of a mirrored configura-
tion, device automatically transforms into a two-way
mirror of device and new_device. If device is part of a
two-way mirror, attaching new_device creates a three-way
mirror, and so on. In either case, new_device begins to
resilver immediately.

-f

Forces use of new_device, even if its appears to be
in use. Not all devices can be overridden in this
manner.

So - when I see (device) (new-device) I generally think of (replacing) a device, not mirroring. This is totally my issue, of course. Perhaps a better syntax would be (source) (target) or something.
Labels:

Comments

Post a Comment

Popular posts from this blog

P2V using dd for KVM-QEMU guest

Preface: I have certainly not exhaustively tested this process.  I had a specific need and found a specific solution that worked. Situation:  I was issued a shiny new laptop running Red Hat Enterprise Linux 7 (with Corp VPN, certs, Authentication configuration, etc...)  The image was great, but I needed more flexibility on my bare metal.  So, my goal was to P2V the corporate image so I could just run it as a VM. * Remove corporate drive and install new SSD * install corp drive in external USB-3 case * Install RHEL 7 on new SSD * dd old drive to a disk-image file in a temp location which will be an image which is the same size as your actual drive (unless you have enough space in your destination to contain a temp and converted image) * convert the raw disk-image to a qcow file while pushing it to the final location - this step should reduce the disk size - however, I believe it will only reduce/collapse zero-byte blocks (not just free space - i.e. if you de...
1 comment
Read more

Sun USS 7100 foo

TIP: put ALL of your LUNs into a designated TARGET and INITIATOR group when you create them.  If you leave them in the "default" group, then everything that does an discovery against the array will find them :-( I'm struggling to recognize a reason that a default should even be present on the array. Also - who, exactly, is Sun trying to kid.  The USS is simply a box.. running Solaris .. with IPMP and ZFS.  Great.  If you have ever attempted to "break-in" or "p0wn" your IBM HMC, you know that there are people out there that can harden a box - then.. there's Sun.  After a recent meltdown at the office I had to get quite intimate with my USS 7110 and learned quite a bit.  Namely: there's a shell ;-) My current irritation is how they attempt to "warn you" away from using the shell (my coverage expired a long time ago to worry about that) and then how they try to hide things, poorly. I was curious as to what version of SunOS it ...
1 comment
Read more

Extending SNMP to run arbitrary shell script

Why are we here... This is not likely something I would have pursued under normal circumstances.  I happen to be working for a customer/client who is not afforded a lot of flexibility to accomplish their goals.  In this case, the rigor is justified.  They have to sometimes be fairly creative with how they solve problems. In this case they would like to utilize an existing snmp implementation to execute a command (or shell script) on a remote system.  They came to me with the idea of using Net-SNMP extend. https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Deployment_Guide/sect-System_Monitoring_Tools-Net-SNMP-Extending.html NOTE:  This is NOT a good implementation strategy in the "real world"  it will simply allow you to test the functionality.  There are a TON of security implications which would need to be taken in to consideration. Implementation Steps: [root@rh7tst01 ~]# yum -y install net-snmp net-snmp-utils ...
Post a Comment
Read more