On Wed, Feb 20, 2013 at 5:46 PM, Bob Friesenhahn < bfrie...@simple.dallas.tx.us> wrote:
> On Thu, 21 Feb 2013, Sašo Kiselkov wrote: > > On 02/21/2013 12:27 AM, Peter Wood wrote: >> >>> Will adding another vdev hurt the performance? >>> >> >> In general, the answer is: no. ZFS will try to balance writes to >> top-level vdevs in a fashion that assures even data distribution. If >> your data is equally likely to be hit in all places, then you will not >> incur any performance penalties. If, OTOH, newer data is more likely to >> be hit than old data >> , then yes, newer data will be served from fewer spindles. In that case >> it is possible to do a send/receive of the affected datasets into new >> locations and then renaming them. >> > > You have this reversed. The older data is served from fewer spindles than > data written after the new vdev is added. Performance with the newer data > should be improved. > > Bob > That depends entirely on how full the pool is when the new vdev is added, and how frequently the older data changes, snapshots, etc. --Tim
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