Re: [ADSM-L] ULTRIUM4C but not 1.6TB
2010-12-09 12:27:04
This is related to a similar question I have been investigating on 3592
media: Why would you ever get less than the native capacity of a
tape?
Does writing compressed data to tape with hardware compression enabled
result in the data expanding?
I always assumed that the hardware compression mechanism would have
something equivalent to "CompressAlways=NO" and detect already
compressed data in its input buffer, however we backup a number of
already compressed file formats and often see FULL tapes with estimated
capacities from 5 to 20% less than the stated native (uncompressed)
capacity.
Can anyone confirm this?
Thanks.
On Thu, 9 Dec 2010 16:30:18 0100, Hans Christian Riksheim wrote:
If a LTO4 tape holds more than 800GB compression is on.
>
> At our place, file data only has a 1.1:1 compression while Oracle data and
> mail is 2.5:1. Overall it is 2:1.
>
> Hans Chr.
>
>
> On Thu, Dec 9, 2010 at 9:18 AM, Mehdi Salehi <ezzobad AT gmail DOT com>
wrote:
>
> > Hi,
> > Drives are LTO4, devclass is ULTRIUM4C, but all "Full" volumes
are between
> > 800GB to 1TB. Is it normal? It seems TSM does not use compression.
> >
> > Mehdi
> >
>
>
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