On Thu, 2010-10-21 at 17:09 -0700, Richard Elling wrote: > On Oct 21, 2010, at 6:19 AM, Eff Norwood wrote: > > Let me frame this in the context specifically of VMWare ESXi 4.x. If I > > create a zvol and give it to ESXi via iSCSI our experience has been that it > > is very fast and guest response is excellent. If we use NFS without a zil > > (we use DDRdrive X1==awesome) because VMWare uses sync (Stable = FSYNC) > > writes NFS performance is not very good. Once we enable our zil > > accelerator, NFS performance is approximately as fast as iSCSI. Enabling or > > disabling the zil has no measurable impact on iSCSI performance for us. > > > > Does a zvol use the zil then or not? If it does, then iSCSI performance > > seems like it should also be slower without a zil accelerator but it's not. > > If it doesn't, then is it true that if the power goes off when I'm doing a > > write to iSCSI and I have no battery backed HBA or RAID card I'll lose data? > > The risk here is not really different that that faced by normal disk drives > which have > nonvolatile buffers (eg virtually all HDDs and some SSDs). This is why > applications > can send cache flush commands when they need to ensure the data is on the > media. > -- richard >
I think you mean "volatile buffers", right? You'll lose data if you HD or SSD has a volatile buffer (almost always DRAM chips with no battery or supercapacitor). -- Erik Trimble Java System Support Mailstop: usca22-317 Phone: x67195 Santa Clara, CA Timezone: US/Pacific (GMT-0800) _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
