Re: Request to share information regarding postgresql pg_xlog file.

Dear John,

Thanks for your support.

>as far as how do you determine whats wrong with your file system?
I tried fsck and hardware check using SMART disk info, no issue found with disk or filesystem.

>what file system are you using for the volume containing the postgres data directory ? with RHEL5, you were pretty much limited to EXT3, I guess ?
File system is ext3 and mount with sync type (rw,sync,dirsync,noatime).

>It would probably be a good idea to unmount the volume and fsck it. also check your system logs for any disk IO errors.
I did that, fsck runs fine no issue.

>is this storage on a raid controller, or using software raid, or just a simple file system on a single disk, or what?
We are using a simple files system which is mirrored at block level.

>desktop/consumer disk drives are notorious for lying about writeback caching, telling the software the data is written when its still in a cache on the drive... if the power fails before the data actually gets written to disk with one of these, you can lose stuff.

Sync mode of file system ensures that, data is continuously flushed on disk as soon as write system call initiated on file system.

Thanks,
Yogesh

From: pgsql-general-owner(at)postgresql(dot)org [mailto:pgsql-general-owner(at)postgresql(dot)org] On Behalf Of John R Pierce
Sent: Thursday, September 15, 2016 1:24 PM
To: pgsql-general(at)postgresql(dot)org
Subject: Re: [GENERAL] Request to share information regarding postgresql pg_xlog file.

On 9/15/2016 12:25 AM, Yogesh Sharma wrote:
Dear John,

Thanks for your support.

Please find below name of rpm.
RPMS/postgresql-8.1.18-2.1.x86_64.rpm
RPMS/postgresql-devel-8.1.18-2.1.x86_64.rpm
RPMS/postgresql-libs-8.1.18-2.1.x86_64.rpm
RPMS/postgresql-python-8.1.18-2.1.x86_64.rpm
RPMS/postgresql-server-8.1.18-2.1.x86_64.rpm

We are using redhat Enterprise Linux 5.8.

ok, those RPM's were built and packaged by Redhat, I believe. If you have a RHEL support contract, you should be able to get help from them. If you don't, you really shouldn't be running RHEL as there's no updates available without one.

as far as how do you determine whats wrong with your file system? I don't know how you'd narrow that down, but postgres expected a file to be there, and it wasn't. what file system are you using for the volume containing the postgres data directory ? with RHEL5, you were pretty much limited to EXT3, I guess ? It would probably be a good idea to unmount the volume and fsck it. also check your system logs for any disk IO errors. is this storage on a raid controller, or using software raid, or just a simple file system on a single disk, or what? desktop/consumer disk drives are notorious for lying about writeback caching, telling the software the data is written when its still in a cache on the drive... if the power fails before the data actually gets written to disk with one of these, you can lose stuff.

--

john r pierce, recycling bits in santa cruz