[p4] Backup scripts?

[Weintraub, David]

Sorry about the late reply, but I need to point out a few things:

In order for us to get the ClearCase snapshot, we had to lock down the
ClearCase database first. The lock guaranteed that the ClearCase
database was in a stable state. This "snapshot" lock lasted less than
four or five minutes while locking for backing up for the entire backup
took the entire night.

The same would apply with Perforce. You'd need to "lock" the Perforce
server to prevent changes. That probably means bringing down, taking the
snapshot, and then bringing it up again. Otherwise, you could get a
snapshot in the middle of a transaction.

Also, NetApps is an NFS solution, and Perforce officially prefers local
storage and not NFS -- especially on the database portion of the depot.

Backing up a database is extremely tricky, no matter how good the OS
since the OS has no way of knowing the actual state of the database when
it attempts to read it. That information is held by the database
application which controls the access to it. It isn't unusual for the
database to hold many changes in memory before writing it to the disk,
so that the disk image may rarely be in a stable state. That's why
almost all database applications or applications with built in databases
have very specific directions for backing them up.

Compared to a lot of them, Perforce is very simple and doesn't require a
complete shutdown of the database. Even better, while StarTeam and
ClearCase require the lock to be held while the non-database portion of
the data is being backed up, Perforce allows the lock to be released
once the database is backed up. Many times, taking down the database,
and backing it takes less time and causes fewer delays than check
pointing live.

The problem is that the checkpoint is universal in nature. It is
hardware independent while the database is very hardware specific. If
you backup the database off of a Solaris server, and suddenly need to
restore it on a Linux server, you may be out of luck. But, you could do
that with a checkpoint.


-----Original Message-----
From: perforce-user-bounces at perforce.com
[mailto:perforce-user-bounces at perforce.com] On Behalf Of Arnt
Gulbrandsen
Sent: Monday, September 25, 2006 11:01 AM
To: perforce-user at perforce.com
Subject: Re: [p4] Backup scripts?

Stephen Vance writes:
> I always use checkpoints for the simple reason that if I care enough 
> about my CM to get a tool like Perforce, I should care about the 
> transactional integrity of my backups. Compressed checkpoints are 
> relatively small and scale with the size of the site.

IMO that's also good enough reason to use a file system that offers
snapshots. David Weintraub mentioned netapp just now.

Arnt
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