Rory Campbell-Lange wrote:

> I've enabled hardware compression and throughput speed has improved to
> around 80MB/sec which is better but still not fantastic. It is coming
> off disk at around 90-100MB/sec so the diffence must be partly down to
> the hw compression.

On my LTO4 I see variations in tape write speed, with HW compression, 
reading from a large direct attached RAID5, of  50 - 195MB/s depending 
on how compressable the data is and how small the files are - larger 
ones writing faster.

> As a matter of interest, is hardware compression an issue if the data
> needs to come off these tapes onto another LTO4 drive? It is important
> that this data can be read for a long time into the future.

No, it is part of the LTO standard and is implemented identically on all 
LTO drives. The algorithm used is also quite clever in that after 
compressing the data and prior to writing, it compares the size to the 
uncompressed input data. If it ends up larger (as will be the case often 
with binary material) it will write the uncompressed data instead, 
therby conserving space.

Regards,

Richjard

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