Server Fault Stack Exchange
Server Fault Stack Exchange

Questions tagged [data-consistency]

18 questions
38
votes
3 answers

When is fsck dangerous?

Recently I've seen the root filesystem of a machine in a remote datacenter get remounted read-only, as a result of consistency issues. On reboot, this error was shown: UNEXPECTED INCONSISTENCY: RUN fsck MANUALLY (i.e., without -a or -p…
0x5C91
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10
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1 answer

Why does yum index get corrupted?

Occasionally yum's cache gets corrupted and we see errors like this: error: db3 error(-30974) from dbenv->failchk: DB_RUNRECOVERY: Fatal error, run database recovery error: cannot open Packages index using db3 - (-30974) error: cannot open…
TomOnTime
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8
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2 answers

Make consistent copy of maildir

Assuming I'm using Dovecot and it's maildir format to save and access mails on a server. How do I avoid race conditions while copying a maildir? I did read some tutorial about backups and using maildir but it did no see anyone writing about this.…
JojOatXGME
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4
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2 answers

Guaranteeing ACID properties for InnoDB databases

What steps must one take to ensure that an otherwise defaultly-configured InnoDB server is truly ACID compliant? The InnoDB configuration page mentions that the hardware itself must be configured to honor fsync calls, i.e. disable any write-back…
plinehan
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2
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3 answers

How to avoid downtime when a need arises to check & fix a huge filesystem

I'm researching for ways to build and run a huge storage server (must be running Linux) where for all data arrays I can run consistency check and fix, while the usual applications using the arrays (reads and writes) keep on working as usual. Say you…
Ján Lalinský
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2
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1 answer

What are storage consistency groups?

Can anyone explain to me what 'consistency groups' are in the context of storage solutions? How can I use them in the real world? It seems every vendor has its own proprietary terminology for storage features, but here's what I could gather so…
user986730
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2
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1 answer

OpenStack EC2 Ubuntu cloud image -- SSH host keys were changed after emegency reboot

Recently one of our servers was hanged due to IPMI BMC failure. It is CentOS 6.3 OpenStack compute host serving KVM vitual machines with qcow2 backend. There was running a VM based on EC2 Ubintu could image…
Veniamin
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2
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3 answers

zfs on a single device: what happens when a file is corrupted?

It is written everywhere that ZFS is helpful even if you only have one physical device, because it will tell you about data corruption due to bit decay and such. However, can it actually address such corruption? In other words, are there any notable…
cnst
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2
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1 answer

Is an SQL Server (Express 2008 R2) database operational during backup? How about consistency?

I am expecting to have a long backup on a certain database and I was wondering if the application can access (read only? read/write?) it while it is being backed up. If read/write access would be available then how will consistency be achieved?…
Andrei Rînea
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1
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0 answers

ZFS: FS consistency with partial disk backups

Suppose I have a zpool with a single disk and some datasets, some files written to them, and a snapshot snap-1. Now I create a raw image t-1.img of the disk. Afterwards, I write some more files, create another snapshot snap-2 and create a new image…
NiklasG
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4 answers

file-system incremental backup - ideally with no downtime for the web site

I am trying to design a web site with backup in mind. Large media elements would be stored on the file system and a daily backup would be done both for the DB and the file-system (which would hold the media elements). While backing up the DB seems…
Andrei Rînea
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1
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3 answers

Is NFS capable of preserving order of operations?

I have a diskless host 'A', that has a directory NFS mounted on server 'B'. A process on A writes to two files F1 and F2 in that directory, and a process on B monitors these files for changes. Assume that B polls for changes faster than A is…
JustJeff
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1
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2 answers

How to ensure DNS records consistency between primary DNS servers?

Root DNS servers may be the most typical primary(not read-only) DNS servers. There are currently 13 IP addresses for root DNS servers; however, considering the IP anycast technology, more than 13 root DNS servers are deployed worldwide. If someone…
da_miao_zi
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1
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1 answer

Data consistency in SQL AlwaysOn Availability Group

I have an AlwaysOn cluster of SQL Server 2019, containing an Availability Group of 3 replicas in Synchronous mode. According to Microsoft documentation: The secondary replica hardens the log and returns an acknowledgement to the primary…
Cat Mucius
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1
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2 answers

How to test Snapraid data corruption?

I'm running Snapraid on my hard drives. However, I want to test it's data integrity features, to see how/if they actually work. But I don't really understand how to 'corrupt' my data. I can just manually change the contents of my files. However,…
RazorHail
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