Edward Ned Harvey
2010-Mar-02 20:36 UTC
[zfs-discuss] How to disable ZIL and benchmark disk speed irresponsibly
I have a system with a bunch of disks, and I?d like to know how much faster it would be if I had an SSD for the ZIL; however, I don?t have the SSD and I don?t want to buy one right now. The reasons are complicated, but it?s not a cost barrier. Naturally I can?t do the benchmark right now... But if I could create a RAM device, and use that for ZIL, of course it would be irresponsible, but I have no data on the system yet, and this is all just to establish the upper bound of what performance could be if I had the SSD. After doing the benchmark, I would reformat the machine anyway. Can I create a ram device and use it for the ZIL? Can I somehow disable the ZIL in an irresponsible way, to establish the upper bound for performance on my system? Thanks... -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.opensolaris.org/pipermail/zfs-discuss/attachments/20100302/bf203b89/attachment.html>
Richard Elling
2010-Mar-02 20:56 UTC
[zfs-discuss] How to disable ZIL and benchmark disk speed irresponsibly
On Mar 2, 2010, at 12:36 PM, Edward Ned Harvey wrote:> I have a system with a bunch of disks, and I?d like to know how much faster it would be if I had an SSD for the ZIL; however, I don?t have the SSD and I don?t want to buy one right now. The reasons are complicated, but it?s not a cost barrier. Naturally I can?t do the benchmark right now... > > But if I could create a RAM device, and use that for ZIL, of course it would be irresponsible, but I have no data on the system yet, and this is all just to establish the upper bound of what performance could be if I had the SSD. After doing the benchmark, I would reformat the machine anyway. > > Can I create a ram device and use it for the ZIL?Yes, see ramdiskadm(1m)> Can I somehow disable the ZIL in an irresponsible way, to establish the upper bound for performance on my system?Yes, but performance achieved by disabling the ZIL is always better, so it seems like an unachievable goal. -- richard ZFS storage and performance consulting at http://www.RichardElling.com ZFS training on deduplication, NexentaStor, and NAS performance http://nexenta-atlanta.eventbrite.com (March 16-18, 2010)