Solaris ZFS & Cyrus : BugID 6535160

[Pascal Gienger]

Vincent Fox <vbfox at ucdavis.edu> wrote:

> With ZFS there are a number of hits with fdsync bugids.  This connects
> back to I believe Pascal Giengers' thread, which I think resulted in him
> turning off ZIL to bump up performance.  This is speculation at this
> point, anyhow here's the BugID information for those what's interested:

I did not turn off ZIL because I did not want to bump my head out... 
Turning off ZIL is not a very good idea. You see, every file system can be 
tuned to be fast turning off all what does guarantee its consistency. 
Nevertheless I did not want to have a fast mail storage which is completely 
unreliable ;-)

The zil lock problem appeared once but disappeared completely like a 
miracle.
I have reasonable figures now on our servers doing reconfiguration on the 
storage side, it appeared to be a random i/o problem on storage, and Cyrus 
is _HEAVY_ random i/o. Not huge data rates but huge seek rates.

You can give your storage system some hints, writes do appear in ZFS as 
sequential ones. Blocks are written in a sequential way  (due to COW), but 
are read in a random way (for sure).