[SERVER-16612] Implicitly zeroed files in WiredTiger Created: 19/Dec/14 Updated: 15/May/19 Resolved: 15/May/19 |
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| Status: | Closed |
| Project: | Core Server |
| Component/s: | Storage |
| Affects Version/s: | None |
| Fix Version/s: | None |
| Type: | Task | Priority: | Major - P3 |
| Reporter: | Bruce Lucas (Inactive) | Assignee: | Donald Anderson |
| Resolution: | Done | Votes: | 0 |
| Labels: | SEKB | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Issue Links: |
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| Sprint: | Storage Engines 2019-05-20 | ||||||||
| Participants: | |||||||||
| Story Points: | 5 | ||||||||
| Description |
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There is a problem with the implicit zeroing of files by the kernel on certain platforms - see The purpose of this ticket is to determine:
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| Comments |
| Comment by Donald Anderson [ 15/May/19 ] |
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I think we're all in agreement here, I'm closing this. |
| Comment by Susan LoVerso [ 15/May/19 ] |
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Several years ago I added the log=(zero_fill=true) specifically in response to this ticket as part of Of course, that configuration setting puts the burden on the user to know to turn it on, but there is a path to mitigate the problem. And like everyone has said, we've never seen the problem actually manifest itself. |
| Comment by Keith Bostic (Inactive) [ 15/May/19 ] |
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I think it's unlikely, but possible, we could be fooled by a file that contained data from a different WiredTiger database, or the reuse of deleted blocks from the current WiredTiger database. Because we store block information outside of the file's blocks (that is, block location and other information is stored separately from the file block itself), I think it less likely we'd be fooled in a data file (with the exception of when we ignore that separate information as part of performing a salvage on the file, as donald.anderson suggested). Because log files don't have a separation between blocks and block information, I think it's more likely we could be fooled in a log file, but still, I think we're likely to detect a problem and panic. That said, I'm strongly of the same opinion as Don – this ticket was filed in response to a kernel bug from 5 years ago that fired on specific Linux releases running on VMWare using virtual SCSI disks managed by LVM, and which we've never seen in a WiredTiger install. I think we should close this one until we see a failure. |