Date: Tue, 11 Oct 2011 17:25:41 -0600 (MDT) From: Dennis Glatting <freebsd@penx.com> To: freebsd-fs@freebsd.org Subject: ZFS/compression/performance Message-ID: <alpine.BSF.2.00.1110111710210.12895@Elmer.dco.penx.com>
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I would appreciate someone knowledgeable in ZFS point me in the right
direction.
I have several ZFS arrays, some using gzip for compression. The compressed
arrays hold very large text documents (10MB->20TB) and are highly
compressible. Reading the files from a compressed data sets is fast with
little load. However, writing to the compressed data sets incurs
substantial load on the order of a load average from 12 to 20.
My questions are:
1) Why such a heavy load on writing?
2) What kind of limiters can I put into effect to reduce load
without impacting compressibilty? For example, is there some
variable to controls the number of parallel compression
operations?
I have a number of different systems. Memory is 24GB on each of the two
large data systems, SSD (Revo) for cache, and a SATA II ZIL. One system is
a 6 core i7 @ 3.33 GHz and the other 4 core ii7 @ 2.93 GHz. The arrays are
RAIDz using cheap 2TB disks.
Thanks.
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