[Veritas-vx] What happens if Log Plex fails?

[Sig Pam - ITServ GmbH]

Hi Veritas-Gurus!

I'm wondering what will happen when a log plex failes.

The Volume is span over two disk subsystems, and looks something like this:


v myVolume
pl myVolume-01
sd storage1-01
pl myVolume-02
sd storage2-01
pl myVolume-03 LOGONLY
sd storage2-01


The volume spans two storage subsystems, namely storage1 and storage2.
The Log-Plex myVolume-03 also uses storage located on storage2.

If storage1 failes, everything is clear: the mirror breaks, the Log keeps
track what has to be resync'ed.

But will the volume be still online when storage2 failes?


Thank your for your input,

Sigmund

[William Havey]

In the event of a log plex failure the volume remains online. Logging a
mirrored volume is optional. So, its failure would not affect the State of
the volume.

As to the comment included when storage1 fails, that the log tracks regions
to be resynced, I don't believe this is correct. A plex failure will require
a complete resync when it is brought back online. The DRL bitmap is
referenced after a system crash to limit what needs to be copied between
plexes.

Post by Sig Pam - ITServ GmbH
Hi Veritas-Gurus!
I'm wondering what will happen when a log plex failes.
v myVolume
pl myVolume-01
sd storage1-01
pl myVolume-02
sd storage2-01
pl myVolume-03 LOGONLY
sd storage2-01
The volume spans two storage subsystems, namely storage1 and storage2.
The Log-Plex myVolume-03 also uses storage located on storage2.
If storage1 failes, everything is clear: the mirror breaks, the Log keeps
track what has to be resync'ed.
But will the volume be still online when storage2 failes?
Thank your for your input,
Sigmund
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[Hudes, Dana]

What is the distinction between DRL and DCO log?
Then there's a RAID5 log which is different.
In terms of reliability, I can I believe mirror a DRL but the DCO shows up concat even if I give it 2 disks ; ditto raid5 log.

[William Havey]

A DRL log tracks differences between two plexes.
A DCO log tracks differences between a volume and its snapshot.
A DCM log (used in VVR) tracks differences between two volumes.

A RAID5 log contains data. It is not a bitmap. Also, it does not appear as a
"LOGONLY" plex. In the State column of vxprint output it reports as "LOG".
And, a R5 volume's log is associated by default. You'd have to delete the
log deliberately.
A DRL, DCO, and DCM logs are bitmaps. Performance is a non-issue with bits.

Post by Hudes, Dana
What is the distinction between DRL and DCO log?
Then there’s a RAID5 log which is different.
In terms of reliability, I can I believe mirror a DRL but the DCO shows up
concat even if I give it 2 disks ; ditto raid5 log.