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Date:      Wed, 27 Jun 2012 12:15:10 +0300
From:      Levent Serinol <lserinol@gmail.com>
To:        freebsd-fs@freebsd.org
Subject:   ZFS stalls on Heavy I/O
Message-ID:  <CACqg54Si-vHFAVkjpTS40MZt4E1Kn14kDUFKmVb8vx449fCnFw@mail.gmail.com>

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Hi,

 Under heavy I/O load we face freeze problems on ZFS volumes on both
Freebsd 9 Release and 10 Current versions. Machines are HP servers (64bit)
with HP Smart array 6400 raid controllers (with battery units). Every da
device is a hardware raid5 where each one includes 9x300GB 10K SCSI hard
drivers. Main of I/O pattern happens on local system except some small NFS
I/O from some other servers (NFS lookup/getattr/ etc.). These servers are
mail servers (qmail) with small I/O patterns (64K Read/Write).  Below you
can  find procstat output on freeze time. write_limit is set to 200MB
because of the huge amount of txg_wait_opens observed before. Every process
stops on D state I think due to txg queue and other 2 queues are full. Is
there any suggestion to fix the problem ?

btw inject_compress is the main process injecting emails to user inboxes
(databases). Also, those machines were running without problems on
Linux/XFS filesystem. For a while ago, we started  migration from Linux to
Freebsd


http://pastebin.com/raw.php?i=ic3YepWQ



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