[gpfsug-discuss] Spectrum Scale 5 and Reading Compressed Data

[Alec]

We have AIX and Spectrum Scale 5.1 and are compressing older data.

We can compress data at about 10GB/minute and decompress data wicked fast
using mmchattr, when a user reads data from a compressed file via
application open / read calls.... it moves at about 5MB/s.  Normally our
I/O pipeline allows for 2400MB/s on a single file read.

What can we look at to speed up the read of the compressed data, are there
any tunables that might affect this?

As it is now if the backup daemon is backing up a compressed file, it can
get stuck for hours, I will go and mmchattr to decompress the file, within
a minute the file is decompressed, and backed up, then I simply recompress
the file once backup has moved on.

Any advice on how to improve the compressed reads under AIX would be very
helpful.

Alec
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