Richard Elling writes: > Ian Collins wrote: >> Richard Elling writes: >>> >>> I think the proposed timeouts here are too short, but the idea has >>> merit. Note that such a preemptive read will have negative performance >>> impacts for high-workload systems, so it will not be a given that people >>> will want this enabled by default. Designing such a proactive system >>> which remains stable under high workloads may not be trivial. >> >> Isn't this how things already work with mirrors? By this I mean requests >> are issued to all devices and if the first returned data is OK, the >> others are not required. > > No. Yes. Sometimes. The details on choice of read targets varies by > implementation. I've seen some telco systems which work this way, > but most of the general purpose systems will choose one target for > the read based on some policy: round-robin, location, etc. This way > you could get the read performance of all disks operating concurrently.
Would it be possible to get ZFS to work the way I described? I was looking at using an exported iSCSI target from a machine in another building to mirror a fileserver with a mainly (>95%) read workload. A first back read implementation would be a good fit for that situation. Ian _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
