Date: Wed, 27 Apr 2016 15:14:36 +0100 From: Gary Palmer <gpalmer@freebsd.org> To: Gerrit K?hn <gerrit.kuehn@aei.mpg.de> Cc: freebsd-fs@freebsd.org Subject: Re: zfs on nvme: gnop breaks pool, zfs gets stuck Message-ID: <20160427141436.GA60370@in-addr.com> In-Reply-To: <20160427152244.ff36ff74ae64c1f86fdc960a@aei.mpg.de> References: <20160427152244.ff36ff74ae64c1f86fdc960a@aei.mpg.de>
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On Wed, Apr 27, 2016 at 03:22:44PM +0200, Gerrit K?hn wrote: > Hello all, > > I have a set of three NVME-ssds on PCIe-converters: > > --- > root@storage:~ # nvmecontrol devlist > nvme0: SAMSUNG MZVPV512HDGL-00000 > nvme0ns1 (488386MB) > nvme1: SAMSUNG MZVPV512HDGL-00000 > nvme1ns1 (488386MB) > nvme2: SAMSUNG MZVPV512HDGL-00000 > nvme2ns1 (488386MB) > --- > > > I want to use a z1 raid on these and created 1m-aligned partitions: > > --- > root@storage:~ # gpart show > => 34 1000215149 nvd0 GPT (477G) > 34 2014 - free - (1.0M) > 2048 1000212480 1 freebsd-zfs (477G) > 1000214528 655 - free - (328K) > > => 34 1000215149 nvd1 GPT (477G) > 34 2014 - free - (1.0M) > 2048 1000212480 1 freebsd-zfs (477G) > 1000214528 655 - free - (328K) > > => 34 1000215149 nvd2 GPT (477G) > 34 2014 - free - (1.0M) > 2048 1000212480 1 freebsd-zfs (477G) > 1000214528 655 - free - (328K) > --- > > > After creating a zpool I recognized that it was using ashift=9. I vaguely > remembered that SSDs usually have 4k (or even larger) sectors, so I > destroyed the pool and set up gnop-providers with -S 4k to get ashift=12. > This worked as expected: > > --- > pool: flash > state: ONLINE > scan: none requested > config: > > NAME STATE READ WRITE CKSUM > flash ONLINE 0 0 0 > raidz1-0 ONLINE 0 0 0 > gpt/flash0.nop ONLINE 0 0 0 > gpt/flash1.nop ONLINE 0 0 0 > gpt/flash2.nop ONLINE 0 0 0 > > errors: No known data errors > --- > > > This pool can be used, exported and imported just fine as far as I can > tell. Then I exported the pool and destroyed the gnop-providers. When > starting with "advanced format" hdds some years ago, this was the way to > make zfs recognize the disks with ashift=12. However, destroying the > gnop-devices appears to have crashed the pool in this case: > > --- > root@storage:~ # zpool import > pool: flash > id: 4978839938025863522 > state: ONLINE > status: One or more devices contains corrupted data. > action: The pool can be imported using its name or numeric identifier. > see: http://illumos.org/msg/ZFS-8000-4J > config: > > flash ONLINE > raidz1-0 ONLINE > 11456367280316708003 UNAVAIL corrupted > data gptid/55ae71aa-eb84-11e5-9298-0cc47a6c7484 ONLINE > 6761786983139564172 UNAVAIL corrupted > data > --- > > > How can the pool be online, when two of three devices are unavailable? I > tried to import the pool nevertheless, but the zpool command got stuck in > state tx-tx. "soft" reboot got stuck, too. I had to push the reset button > to get my system back (still with a corrupt pool). I cleared the labels > and re-did everything: the issue is perfectly reproducible. > > Am I doing something utterly wrong? Why is removing the gnop-nodes > tampering with the devices (I think I did exactly this dozens of times on > normal hdds during that previous years, and it always worked just fine)? > And finally, why does the zpool import fail without any error message and > requires me to reset the system? > The system is 10.2-RELEASE-p9, update is scheduled for later this week > (just in case it would make sense to try this again with 10.3). Any other > hints are most welcome. Did you destroy the gnop devices with the pool online? In the procedure I remember you export the pool, destroy the gnop devices, and then reimport the pool. Also, you only need to do the gnop trick for a single device in the pool for the entire pool's ashift to be changed AFAIK. There is a sysctl now too vfs.zfs.min_auto_ashift which lets you manage the ashift on a new pool without having to try the gnop trick Regards, Gary
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