Steven Hartland
2019-Apr-20 15:50 UTC
Concern: ZFS Mirror issues (12.STABLE and firmware 19 .v. 20)
Have you eliminated geli as possible source? I've just setup an old server which has a LSI 2008 running and old FW (11.0) so was going to have a go at reproducing this. Apart from the disconnect steps below is there anything else needed e.g. read / write workload during disconnect? mps0: <Avago Technologies (LSI) SAS2008> port 0xe000-0xe0ff mem 0xfaf3c000-0xfaf3ffff,0xfaf40000-0xfaf7ffff irq 26 at device 0.0 on pci3 mps0: Firmware: 11.00.00.00, Driver: 21.02.00.00-fbsd mps0: IOCCapabilities: 185c<ScsiTaskFull,DiagTrace,SnapBuf,EEDP,TransRetry,IR> ??? Regards ??? Steve On 20/04/2019 15:39, Karl Denninger wrote:> I can confirm that 20.00.07.00 does *not* stop this. > The previous write/scrub on this device was on 20.00.07.00.? It was > swapped back in from the vault yesterday, resilvered without incident, > but a scrub says.... > > root at NewFS:/home/karl # zpool status backup > ? pool: backup > ?state: DEGRADED > status: One or more devices has experienced an unrecoverable error.? An > ??????? attempt was made to correct the error.? Applications are unaffected. > action: Determine if the device needs to be replaced, and clear the errors > ??????? using 'zpool clear' or replace the device with 'zpool replace'. > ?? see: http://illumos.org/msg/ZFS-8000-9P > ? scan: scrub repaired 188K in 0 days 09:40:18 with 0 errors on Sat Apr > 20 08:45:09 2019 > config: > > ??????? NAME????????????????????? STATE???? READ WRITE CKSUM > ??????? backup??????????????????? DEGRADED???? 0???? 0???? 0 > ????????? mirror-0??????????????? DEGRADED???? 0???? 0???? 0 > ??????????? gpt/backup61.eli????? ONLINE?????? 0???? 0???? 0 > ??????????? gpt/backup62-1.eli??? ONLINE?????? 0???? 0??? 47 > ??????????? 13282812295755460479? OFFLINE????? 0???? 0???? 0? was > /dev/gpt/backup62-2.eli > > errors: No known data errors > > So this is firmware-invariant (at least between 19.00.00.00 and > 20.00.07.00); the issue persists. > > Again, in my instance these devices are never removed "unsolicited" so > there can't be (or at least shouldn't be able to) unflushed data in the > device or kernel cache.? The procedure is and remains: > > zpool offline ..... > geli detach ..... > camcontrol standby ... > > Wait a few seconds for the spindle to spin down. > > Remove disk. > > Then of course on the other side after insertion and the kernel has > reported "finding" the device: > > geli attach ... > zpool online .... > > Wait... > > If this is a boogered TXG that's held in the metadata for the > "offline"'d device (maybe "off by one"?) that's potentially bad in that > if there is an unknown failure in the other mirror component the > resilver will complete but data has been irrevocably destroyed. > > Granted, this is a very low probability scenario (the area where the bad > checksums are has to be where the corruption hits, and it has to happen > between the resilver and access to that data.)? Those are long odds but > nonetheless a window of "you're hosed" does appear to exist. >
Karl Denninger
2019-Apr-20 17:35 UTC
Concern: ZFS Mirror issues (12.STABLE and firmware 19 .v. 20)
On 4/20/2019 10:50, Steven Hartland wrote:> Have you eliminated geli as possible source?No; I could conceivably do so by re-creating another backup volume set without geli-encrypting the drives, but I do not have an extra set of drives of the capacity required laying around to do that.? I would have to do it with lower-capacity disks, which I can attempt if you think it would help.? I *do* have open slots in the drive backplane to set up a second "test" unit of this sort.? For reasons below it will take at least a couple of weeks to get good data on whether the problem exists without geli, however.> > I've just setup an old server which has a LSI 2008 running and old FW > (11.0) so was going to have a go at reproducing this. > > Apart from the disconnect steps below is there anything else needed > e.g. read / write workload during disconnect?Yes.? An attempt to recreate this on my sandbox machine using smaller disks (WD RE-320s) and a decent amount of read/write activity (tens to ~100 gigabytes) on a root mirror of three disks with one taken offline did not succeed.? It *reliably* appears, however, on my backup volumes with every drive swap.? The sandbox machine is physically identical other than the physical disks; both are Xeons with ECC RAM in them. The only operational difference is that the backup volume sets have a *lot* of data written to them via zfs send|zfs recv over the intervening period where with "ordinary" activity from I/O (which was the case on my sandbox) the I/O pattern is materially different.? The root pool on the sandbox where I tried to reproduce it synthetically *is* using geli (in fact it boots native-encrypted.) The "ordinary" resilver on a disk swap typically covers ~2-3Tb and is a ~6-8 hour process. The usual process for the backup pool looks like this: Have 2 of the 3 physical disks mounted; the third is in the bank vault. Over the space of a week, the backup script is run daily.? It first imports the pool and then for each zfs filesystem it is backing up (which is not all of them; I have a few volatile ones that I don't care if I lose, such as object directories for builds and such, plus some that are R/O data sets that are backed up separately) it does: If there is no "... at zfs-base": zfs snapshot -r ... at zfs-base; zfs send -R ... at zfs-base | zfs receive -Fuvd $BACKUP else zfs rename -r ... at zfs-base ... at zfs-old zfs snapshot -r ... at zfs-base zfs send -RI ... at zfs-old ... at zfs-base |zfs recv -Fudv $BACKUP .... if ok then zfs destroy -vr ... at zfs-old otherwise print a complaint and stop. When all are complete it then does a "zpool export backup" to detach the pool in order to reduce the risk of "stupid root user" (me) accidents. In short I send an incremental of the changes since the last backup, which in many cases includes a bunch of automatic snapshots that are taken on frequent basis out of the cron.? Typically there are a week's worth of these that accumulate between swaps of the disk to the vault, and the offline'd disk remains that way for a week.? I also wait for the zpool destroy on each of the targets to drain before continuing, as not doing so back in the 9 and 10.x days was a good way to stimulate an instant panic on re-import the next day due to kernel stack page exhaustion if the previous operation destroyed hundreds of gigabytes of snapshots (which does routinely happen as part of the backed up data is Macrium images from PCs, so when a new month comes around the PC's backup routine removes a huge amount of old data from the filesystem.) Trying to simulate the checksum errors in a few hours' time thus far has failed.? But every time I swap the disks on a weekly basis I get a handful of checksum errors on the scrub.? If I export and re-import the backup mirror after that the counters are zeroed -- the checksum error count does *not* remain across an export/import cycle although the "scrub repaired" line remains. For example after the scrub completed this morning I exported the pool (the script expects the pool exported before it begins) and ran the backup.? When it was complete: root at NewFS:~/backup-zfs # zpool status backup ? pool: backup ?state: DEGRADED status: One or more devices has been taken offline by the administrator. ??????? Sufficient replicas exist for the pool to continue functioning in a ??????? degraded state. action: Online the device using 'zpool online' or replace the device with ??????? 'zpool replace'. ? scan: scrub repaired 188K in 0 days 09:40:18 with 0 errors on Sat Apr 20 08:45:09 2019 config: ??????? NAME????????????????????? STATE???? READ WRITE CKSUM ??????? backup??????????????????? DEGRADED???? 0???? 0???? 0 ????????? mirror-0??????????????? DEGRADED???? 0???? 0???? 0 ??????????? gpt/backup61.eli????? ONLINE?????? 0???? 0???? 0 ??????????? gpt/backup62-1.eli??? ONLINE?????? 0???? 0???? 0 ??????????? 13282812295755460479? OFFLINE????? 0???? 0???? 0? was /dev/gpt/backup62-2.eli errors: No known data errors It knows it fixed the checksums but the error count is zero -- I did NOT "zpool clear". This may have been present in 11.2; I didn't run that long enough in this environment to know.? It definitely was *not* present in 11.1 and before; the same data structure and script for backups has been in use for a very long time without any changes and this first appeared when I upgraded from 11.1 to 12.0 on this specific machine, with the exact same physical disks being used for over a year (they're currently 6Tb units; the last change out for those was ~1.5 years ago when I went from 4Tb to 6Tb volumes.)? I have both HGST-NAS and He-Enterprise disks in the rotation and both show identical behavior so it doesn't appear to be related to a firmware problem in one disk .vs. the other (e.g. firmware that fails to flush the on-drive cache before going to standby even though it was told to.)> > mps0: <Avago Technologies (LSI) SAS2008> port 0xe000-0xe0ff mem > 0xfaf3c000-0xfaf3ffff,0xfaf40000-0xfaf7ffff irq 26 at device 0.0 on pci3 > mps0: Firmware: 11.00.00.00, Driver: 21.02.00.00-fbsd > mps0: IOCCapabilities: > 185c<ScsiTaskFull,DiagTrace,SnapBuf,EEDP,TransRetry,IR> > > ??? Regards > ??? Steve > > On 20/04/2019 15:39, Karl Denninger wrote: >> I can confirm that 20.00.07.00 does *not* stop this. >> The previous write/scrub on this device was on 20.00.07.00.? It was >> swapped back in from the vault yesterday, resilvered without incident, >> but a scrub says.... >> >> root at NewFS:/home/karl # zpool status backup >> ?? pool: backup >> ??state: DEGRADED >> status: One or more devices has experienced an unrecoverable error.? An >> ???????? attempt was made to correct the error.? Applications are >> unaffected. >> action: Determine if the device needs to be replaced, and clear the >> errors >> ???????? using 'zpool clear' or replace the device with 'zpool replace'. >> ??? see: http://illumos.org/msg/ZFS-8000-9P >> ?? scan: scrub repaired 188K in 0 days 09:40:18 with 0 errors on Sat Apr >> 20 08:45:09 2019 >> config: >> >> ???????? NAME????????????????????? STATE???? READ WRITE CKSUM >> ???????? backup??????????????????? DEGRADED???? 0???? 0???? 0 >> ?????????? mirror-0??????????????? DEGRADED???? 0???? 0???? 0 >> ???????????? gpt/backup61.eli????? ONLINE?????? 0???? 0???? 0 >> ???????????? gpt/backup62-1.eli??? ONLINE?????? 0???? 0??? 47 >> ???????????? 13282812295755460479? OFFLINE????? 0???? 0???? 0? was >> /dev/gpt/backup62-2.eli >> >> errors: No known data errors >> >> So this is firmware-invariant (at least between 19.00.00.00 and >> 20.00.07.00); the issue persists. >> >> Again, in my instance these devices are never removed "unsolicited" so >> there can't be (or at least shouldn't be able to) unflushed data in the >> device or kernel cache.? The procedure is and remains: >> >> zpool offline ..... >> geli detach ..... >> camcontrol standby ... >> >> Wait a few seconds for the spindle to spin down. >> >> Remove disk. >> >> Then of course on the other side after insertion and the kernel has >> reported "finding" the device: >> >> geli attach ... >> zpool online .... >> >> Wait... >> >> If this is a boogered TXG that's held in the metadata for the >> "offline"'d device (maybe "off by one"?) that's potentially bad in that >> if there is an unknown failure in the other mirror component the >> resilver will complete but data has been irrevocably destroyed. >> >> Granted, this is a very low probability scenario (the area where the bad >> checksums are has to be where the corruption hits, and it has to happen >> between the resilver and access to that data.)? Those are long odds but >> nonetheless a window of "you're hosed" does appear to exist. >> >-- Karl Denninger karl at denninger.net <mailto:karl at denninger.net> /The Market Ticker/ /[S/MIME encrypted email preferred]/ -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type: application/pkcs7-signature Size: 4897 bytes Desc: S/MIME Cryptographic Signature URL: <http://lists.freebsd.org/pipermail/freebsd-stable/attachments/20190420/5f025157/attachment.bin>