Re: Faster backups - possibly Solaris pipe buffer size

In article <1149287494.566222.88370@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
<jayl-news@xxxxxxxxxxxxxx> wrote:

Jim Prescott wrote:
If it is possible to disable the tapedrive's compression you should do so.
Trying to compress encrypted (or compressed) data will likely lead to
slight data expansion. It is possible having tapedrive compression
on might be both slowing things down and reducing the tape capacity.

Not on an LTO drive. The drive has substantial on-board buffer RAM
(and substantial compression resources). It slurps a big chunk of input
data into buffer, tries compressing it into another chunk of buffer, if
no joy (guaranteed in this case, because of encryption) it just uses
the original data.

Despite the fact that on board compression usually is designed to be fast
but not best, I suspec that the drive does not have sufficient RAM.
If you like to have best thruoughput on a tape device, you need FIFO RAM
for ~ 30 seconds.

For 80 MB/s this is ~ 2.5 GB of RAM.

If you use star

ftp://ftp.berlios.de/pub/star/alpha/

you may have such a FIFO in case that you have at least 4 GB of RAM
in your computer (to five the filesystem buffering spme spare RAM
in the OS).



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