The impact of compression during backup windows may be significant when you first turn it on. It may have a lot of compressing to do. I mitigated this by setting compression on for images older than 1 year, then the next day set it to 6 months, then 3 months the next day, then 1 month, so the initial "surge" in compression was spread over several days.
If I recall correctly, decompression of the catalog image
occurs before you initate the restore. The catalog image gets
decompressed when you browse it using the restore GUI.
This of course means that doing large searches for files using the GUI
(or command line) can cause your catalog to grow significantly in a
short period of time.
If you are restore from something like RMAN, I guess the decompression would occur when RMAN starts the restore for each image. But any delay should be negligible since the catalog images are so small - just containing one file.
The degree of the impact will of course be highly dependent on how much
processing power you have available on your master server, the I/O throughput to your catalog, and the
number of files in the backup you are trying to restore from.
We compress catalog entries older than about 30 days. Not that we
restore from them often, but when we do, the delay while the image is
decompressed is not noticeable. (But then, the backup/restore GUI is never "snappy" - I guess I am used to the spinning hourglass).
- Dean
On Thu, Jul 17, 2008 at 9:49 AM, Justin Piszcz <
jpiszcz AT lucidpixels DOT com> wrote:
On Wed, 16 Jul 2008, Abhishek Dhingra1 wrote:
> Justin,
>
> What is the impact of doing the restore, does it take more time.if yes,
> then hw much,
>
> We have around 1000 clients in our environment, with no free window.
>
> As per the document , compression run after the each backup session, as we
> dont have any free window, if we configure the compression at what time
> compression will run.
>
> Any suggestion will be appreciated.
Abhishek,
Best to do test restores, it can impact it quite a bit if you are restoring
many small files, up to 10-30 minutes on slower disks & I/O subsystems.
You also need to have enough space to decompress the compressed images.
It depends on the I/O / where the images are stored.
It depends on how many files you are restoring.
Justin.
