RE: Can Disk mirroring/db snapshots replace the usage of taking database backups?
Art,
I must have missed something in this thread... ...
You said "Keep in mind again that if you are not running IDS 11.10 or
later you will not be able to roll forward any logical logs after a
restore" (your orig message is below). On IDS 9.4, after an onmode -c
block (external backup), I have rolled logs forward on a restore. I
must have not quite grasped what you meant, but it is late in my day and
one of my 2 brain cells has already failed over ;)
Thanks,
NJ
-----Original Message-----
From: Art S. Kagel (Oninit) [mailto:art@oninit.com]
Sent: Monday, April 14, 2008 3:32 PM
To: jpierrot@chubb.com
Cc: informix-list@iiug.org; informix-list-bounces@iiug.org; Sebastian,
Norma J.
Subject: Re: Can Disk mirroring/db snapshots replace the usage of taking
database backups?
jpierrot@chubb.com wrote:
>
> *Art,*
> *The snapshots are instantaneous since it uses pointers to the disks
> as explained to me, no data transfer during a snapshot. Ideally, I
> would not want to block the DB every hour, for it will generate a lot
> of calls from the help desk. Those blocks duration must stay within
> what we are getting now with our checkpoints, 0 seconds checkpoint
> average. Anything that is noticeable to the users community is not
> good, it must be transparent. *
>
Be suspicious, be very suspicious. OK, so I'm assuming that the array
is keeping an up-to-date copy on another structure somewhere, like EMC
Symmetrics, and the snapshot operates by breaking that remote mirror,
copying the remote disk off somewhere else, then reestablishing the
remote mirror. To use that kind of snapshot you will have to perform an
'onmode -c block' to make sure that there is a consistent image on the
disks, then request the snapshot which while not instantaneous should
take only a second, then unblock the engine with 'onmode -c unblock'.
Keep in mind again that if you are not running IDS 11.10 or later you
will not be able to roll forward any logical logs after a restore. The
restore will be as of the moment of the 'onmode -c block' checkpoint and
any data modified between then and the crash will be lost. Finally be
aware that until the remote mirror is completely copied (which I
guarantee is not instaneous) you will be operating without that first
line of backup.
Art S. Kagel
Oninit
>
> *Thanks!*
>
> *jp*
> Inactive hide details for "Art S. Kagel (Oninit)" <art@oninit.com>"Art
> S. Kagel (Oninit)" <art@oninit.com>
>
>
> *"Art S. Kagel (Oninit)" <art@oninit.com>*
>
> 04/11/2008 05:14 PM
>
>
>
> To
>
> "Sebastian, Norma J." <NormaJean.Sebastian@tellabs.com>
>
> cc
>
> jpierrot@chubb.com, informix-list@iiug.org,
> informix-list-bounces@iiug.org
>
> Subject
>
> Re: Can Disk mirroring/db snapshots replace the usage oftaking
> database backups?
>
>
>
>
> Sebastian, Norma J. wrote:
>
> I have another concern. You say Falconstor will make a snapshot every
N
> minutes. Do you really want to have the server blocked even once an
> hour for the several minutes it will take to make the snapshot? Or
are
> they claiming that the snapshots are nearly instantaneous? If so, how
> are they doing that? By blocking the DB, breaking some mirror, then
> unblocking the DB, and making a copy of the mirror offline? Where's
> your redundancy until the mirror is reestablished? Or is it a three
way
> mirror? In that case you don't even need Falconstor, you can do the
> three way mirror yourself, script the snapshots/external archives, and
> save a bundle of $$$! There have been IDS users doing that for years!
>
> Art S. Kagel
> Oninit
>
> > JP,
> >
> > if your assumption is right that it uses an "onmode -c block" then
you
> > would have a recoverable/rollforwardable image....
> > IF anything goes wrong during the time the snapshot is taken....
then
> > everybody waits till it is fixed... cuz the DB is blocked... this
> > would appear to be no different than you yourself issuing the
> > block/unblock commands... but if the auto-software (falconstor)
> > introduced between the block/unblock goes haywire for any reason...
> > well... there u are... blocked.. and so are your users.... it would
> > be wise at the least to build some type of monitoring/page-out to
DBAs
> > in the process in the event there is a snag and a manual unblock is
> > needed. (this falconstor should be able to page-out on that)
> >
> > if the software builds in a block/unblock... then it is still in
your
> > best interest to back up the DB logs via informix onbar because it
> > will be onbar, not falconstor, restoring/rolling those logs forward.
> > (same with RMAN i would guess)
> >
> > how big is your database?...
> > how is this software going to make your life any easier?
> > what prevents you from scripting a block/split/unblock yourself
today
> > without this software?...
> > is this software being pushed on you by management?
> >
> > i only have 2 brain cells, but i can't imagine any value in adding
> > this to an IDS system.
> > do they really really support IDS or is that only lip service
because
> > they want u to buy it for oracle and/or sqlserver or something?....
> >
> > some, if not all of your questions should be posed to falconstor....
> > if they truly support informix, they should be able to answer your
> > concerns. if they really want your business, they should help u set
> > it up for free on a free test server to see the value....
> >
> > i searched their web site for informix, it came up with 2 tiny
> > references... one in legal smallprint and the other in a news
> > article... but if you search for oracle or sql server on their
> > site... .. sqlserver has 2 pages of references and oracle has 3
pages.
> >
> > so they really support informix? put the ball in their court to
> > prove it...
> >
> > sorry... feeling critical today...
> > Norma Jean
> >
> >
> >
> >
> >
> >
------------------------------------------------------------------------
> > *From:* informix-list-bounces@iiug.org
> > [mailto:informix-list-bounces@iiug.org] *On Behalf Of
> *jpierrot@chubb.com
> > *Sent:* Friday, April 11, 2008 1:42 PM
> > *To:* Kevin Cherkauer
> > *Cc:* informix-list-bounces@iiug.org; informix-list@iiug.org
> > *Subject:* Re: Can Disk mirroring/db snapshots replace the usage
> > oftaking database backups?
> >
> > There are a few things I need to add to this post:
> > According to the vendor, FalconStor has a built in snapshot agent
for
> > Informix which forces Informix to flush all information to disk and
> > inserts a tag into the data stream being written to disk (presumably
> > at the end of the data being flushed and in front of any new data),
> > per se, the snapshot is consistent as of that point in time. Any
> > update after that doesn't impact the snapshot data.
> >
> > I do not know yet how the snapshot agent triggers Informix to flush
> > everything to disk, but ass