>> >> ZFS will always flush the disk cache at appropriate times. If ZFS >> thinks that is alone it will turn the write cache on the disk on. > > I'm not sure if you're trying to argue or agree. If you're trying to argue, > you're going to have to do a better job than "zfs will always flush disk > cache at appropriate times", because that's outright false in the case where > zfs doesn't own the entire disk. That flush may very well produce an > outcome zfs could never pre-determine.
You can send flush cache commands to the disk how often you wish, the only thing that happens is that the disk writes dirty sectors from its cache to the disk. That is, no writes will be done that should not have happend at some time anyway. This will not harm UFS or any other user of the disk. Other users can issue flush cache command without affecting ZFS. Please read up on what the flus cache command does! ZFS will send flush cache commands even when it is not alone on the disk. There are many disks with write cache on by default. There have even been disks that won't turn it off even if told so. >> > It could cause corruption if you had UFS and zfs on the same disk. >> >> It is safe to have UFS and ZFS on the same disk and it has always been >> safe. > > ***unless you turn on write cache. And without write cache, performance > sucks. Hence me answering the OP's question. There was no mention of cache at all in the question. It was not clear that this sentence reffered to your own text, hence the misunderstanding: "It could cause corruption if you had UFS and zfs on the same disk." I read that as a separate statement. As to the performance sucks, that is putting it a bit harsh, you will get better performance with write cache but the system will be perfectly usable without. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
