On 10 November, 2011 - Bob Friesenhahn sent me these 1,6K bytes: > On Wed, 9 Nov 2011, Tomas Forsman wrote: >>> >>> At all times, if there's a server crash, ZFS will come back along at next >>> boot or mount, and the filesystem will be in a consistent state, that was >>> indeed a valid state which the filesystem actually passed through at some >>> moment in time. So as long as all the applications you're running can >>> accept the possibility of "going back in time" as much as 30 sec, following >>> an ungraceful ZFS crash, then it's safe to disable ZIL (set sync=disabled). >> >> Client writes block 0, server says OK and writes it to disk. >> Client writes block 1, server says OK and crashes before it's on disk. >> Client writes block 2.. waaiits.. waiits.. server comes up and, server >> says OK and writes it to disk. >> >> Now, from the view of the clients, block 0-2 are all OK'd by the server >> and no visible errors. >> On the server, block 1 never arrived on disk and you've got silent >> corruption. > > The silent corruption (of zfs) does not occur due to simple reason that > flushing all of the block writes are acknowledged by the disks and then a > new transaction occurs to start the next transaction group. The previous > transaction is not closed until the next transaction has been > successfully started by writing the previous TXG group record to disk. > Given properly working hardware, the worst case scenario is losing the > whole transaction group and no "corruption" occurs. > > Loss of data as seen by the client can definitely occur.
When a client writes something, and something else ends up on disk - I call that corruption. Doesn't matter whose fault it is and technical details, the wrong data was stored despite the client being careful when writing. /Tomas -- Tomas Forsman, st...@acc.umu.se, http://www.acc.umu.se/~stric/ |- Student at Computing Science, University of Umeå `- Sysadmin at {cs,acc}.umu.se _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
