I did some more checks. I used my adaptec controller administration commands to check for the status. I have 5 logical volumes each on one physical disk. I saw I had the volumes with wcache disabled, but physical disks with cache enabled. So, i used the arcconf command to change the physiscal disks and disable cache. Both each logical volume and each physical disk has Write Cache Disabled (write-through). System was still with zfs_nocacheflush=1, but because disks has no cache at all, I exepcted a slow down, but the machine appeared fast as with cash and zfs_nocacheflush. So I turned nocacheflush=0 again, and I expected no change again, but then I have a slow down.... I'm totally confused...... ---------------------------------------------------------------------------------- Da: Gabriele Bulfon A: Discussion list for OpenIndiana Data: 10 ottobre 2011 12.07.08 CEST Oggetto: Re: [OpenIndiana-discuss] use zfs_nocacheflush Thanx. Yes, I understand the danger, and I have to say I first tried using NFS async, but that made no difference to me. I'm still a bit confused about this nocacheflush flag, though. Does it refers ONLY to controllers/disks cache or to the zfs system cache too? I disabled write cache on every disk in the zpool, through the controller bios. So, I assume there should be no difference between the two flag statuses: I believe the controller should always return "ok, done" once written, because it has no cache at all. Am I wrong? Probably I'm wrong, because the performace increased a lot with nocacheflush=1, so maybe there is other cache involved? Thanx. ---------------------------------------------------------------------------------- Da: Albert Lee A: Discussion list for OpenIndiana Data: 8 ottobre 2011 0.36.02 CEST Oggetto: Re: [OpenIndiana-discuss] use zfs_nocacheflush On Thu, Oct 6, 2011 at 5:45 AM, Gabriele Bulfon wrote: Hi, NFS on zfs can be quite a pain with large number of small files. After playing around it, I discovered this zfs_nocacheflush flag bringing me back to high performances on NFS. Questions: - How much unsafe is this? This is completely unsafe and can easily lead to data loss unless you have a battery-backed cache. This setting determines whether the cache is flushed to complete transactions. NFS operations are synchronous. Use a log device if you want fast synchronous performance, or a mount option on the client to make operations async (if you don't mind losing recent NFS writes in the event of a crash). Disabling atimes may also help. -Albert _______________________________________________ OpenIndiana-discuss mailing list [email protected] http://openindiana.org/mailman/listinfo/openindiana-discuss _______________________________________________ OpenIndiana-discuss mailing list [email protected] http://openindiana.org/mailman/listinfo/openindiana-discuss
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