On Fri, Apr 15, 2016 at 9:26 PM, Richard Yao <r...@gentoo.org> wrote:
> > The first is to make sure that ZFS uses proper alignment on the device. > According to what I learned via Google searches, the Intel DC P3600 > supports both 512-byte sectors and 4096-byte sectors, but is low leveled > formatted to 512-byte sectors by default. You could run fio to see how the > random IO performance differs on 512-byte IOs at 512-byte formatting vs 4KB > IOs at 4KB formatting, but I expect that you will find it performs best in > the 4KB case like Intel's enterprise SATA SSDs do. If the 512-byte random > IO performance was notable, Intel would have advertised it, but they did > not do that: > > > http://www.intel.com/content/dam/www/public/us/en/documents/product-specifications/ssd-dc-p3600-spec.pdf > > http://www.cadalyst.com/%5Blevel-1-with-primary-path%5D/how-configure-oracle-redo-intel-pcie-ssd-dc-p3700-23534 > > So, I played around with this. Intel's isdct tool will let you secure erase the P3600 and set it up as a 4k sector device, or a 512, with a few other options as well. I have to re-look but it might support 8k sectors too. Unfortunately the NVMe driver doesn't play well with the SSD formatted for anything other than 512 byte sectors. I noted my findings in Illumos bug #6912. I need to look at how Illumos partitions the devices if you just feed zpool the device rather than a partition, I didn't look to see if it was aligning things correctly or not on it's own. The second is that it is possible to increase IOPS beyond Intel's > specifications by doing a secure erase, giving SLOG a tiny 4KB aligned > partition and leaving the rest of the device unused. Intel's numbers are > for steady state performance where almost every flash page is dirty. If you > leave a significant number of pages clean (i.e. unused following a secure > erase), the drive should perform better than what Intel claims by virtue of > the internal book keeping and garbage collection having to do less. Anandtech > has benchmarks numbers showing this effect on older consumer SSDs on > Windows in a comparison with the Intel DC S3700: > Using isdct I have mine set to 50% over-provisioning, so they show up as 200GB devices now. As noted in bug 6912 you have to secure erase after changing that setting or the NVMe driver REALLY gets unhappy. Josh C
_______________________________________________ OmniOS-discuss mailing list OmniOS-discuss@lists.omniti.com http://lists.omniti.com/mailman/listinfo/omnios-discuss