Edward Ned Harvey (opensolarisisdeadlongliveopensolaris) wrote:
From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
boun...@opensolaris.org] On Behalf Of Schweiss, Chip
How can I determine for sure that my ZIL is my bottleneck? If it is the
bottleneck, is it possible to keep adding mirrored pairs of SSDs to the ZIL to
make it faster? Or should I be looking for a DDR drive, ZeusRAM, etc.
Temporarily set sync=disabled
Or, depending on your application, leave it that way permanently. I know, for
the work I do, most systems I support at most locations have sync=disabled. It
all depends on the workload.
Noting of course that this means that in the case of an unexpected system
outage or loss of connectivity to the disks, synchronous writes since the last
txg commit will be lost, even though the applications will believe they are
secured to disk. (ZFS filesystem won't be corrupted, but it will look like it's
been wound back by up to 30 seconds when you reboot.)
This is fine for some workloads, such as those where you would start again with
fresh data and those which can look closely at the data to see how far they got
before being rudely interrupted, but not for those which rely on the Posix
semantics of synchronous writes/syncs meaning data is secured on non-volatile
storage when the function returns.
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