Re: Backup Times Strategy?
- From: "John Fullbright" <fjohn@donotspamnetappdotcom>
- Date: Sun, 14 Sep 2008 17:18:32 -0700
What are you using for storage? Which VSS Provider are you using?
Snapshots are a very useful technology, but not all VSS providers are
created equal. If you're using a Copy oin Write provider, there's a pretty
hefty performance penalty for having a snapshot in place. When you take a
COW snapshot, every subsequent overwrite actually costs 3 IOs; read the
original block, write it to the difference area, overwrite the original
block with the changed block. With this type of provider you'll want to
minimize the performance hit by placing the difference area on another
volume, and keep retained snapshots to a minimum.
A VSS full backup, or DPM "Express Full" is a snapshot of both the DBs and
logs. Once you take an express full, you'll want to export it to another
storage device be it disk or tape.
A VSS incremental is a snapshot of the logs. Adding incrementals reduces
your RPO, but arguably increases your RTO because you have to replay the
logs since the last Express full. Again, you would want to export the
snapshot to another device.
If you are using a COW provider, I would look at an Express full once a day
supplemented by incrementals every few hours. Only leave one snapshot in
place on a volume, and only leave it there as log as it takes to get you
data to another media. You can reduce the performance hit by putting the
difference area on another volume. I would recommend D2D or D2D2Tape. By
exporting the snapshot to another disk first, you minimize the time the
snapshot is kept in place.
If you use an Allocate on Write provider, like the Netapp hardware provider,
there is no significant performance penalty for leaving a snapshot in place.
In fact, you can have up to 255 shaps on a volume with only 3% performance
degradation. If you are using an AOW VSS provider, this changes the game.
Since there isn't a performance penalty, you can do express fulls far more
frequently, and leave them in place for long periods of time. You would
only do incrementals is situations where you had a really tight RPO, and
from your description it doesn't sound like that's the case.
"Paul Hutchings" <paul@xxxxxxxxxxx> wrote in message
news:paul-F3AD36.11593214092008@xxxxxxxxxxxxxxxxxxxxxxx
Would appreciate any input into what times people are choosing to run
full and incremental backups.
We have a single Exchange 2003 SP2 box running a Commvault Galaxy
Exchange Database agent with VSS enabled.
Prior to installing the Commvault agent I was simply using ntbackup to
do an Exchange Aware full backup to disk each night, with an incremental
at midday, then streaming these to tape as "dumb" files.
On this server I have multiple storage groups/databases and am planning
on keeping each database (ideally much) below 100gb.
Do people feel it's essential to do full backups every day with
Exchange, or, for example, would a single weekly full backup with
incremental backups every 4 hours seem sensible?
In terms of SLA's I'm not under any in that I don't *have* to get the
box back within an agreed time-scale, but naturally I want to make
things as robust as possible and give myself the best chance of getting
the box back to as recent a state as possible, within the smallest
period of time that I can.
.
- References:
- Backup Times Strategy?
- From: Paul Hutchings
- Backup Times Strategy?
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