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help / color / mirror / Atom feedFrom: Michael Banck <[email protected]>
To: Jakub Wartak <[email protected]>
Cc: Aleksander Alekseev <[email protected]>
Cc: [email protected]
Cc: Tom Lane <[email protected]>
Cc: Frits Hoogland <[email protected]>
Subject: Re: The ability of postgres to determine loss of files of the main fork
Date: Wed, 1 Oct 2025 14:15:52 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAKZiRmy0CK3m0-raCdTDELg0JjY7qAqzEN9P5n4N4wGw6ys4tw@mail.gmail.com>
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Hi,
On Wed, Oct 01, 2025 at 02:05:53PM +0200, Jakub Wartak wrote:
> On Wed, Oct 1, 2025 at 1:46 PM Aleksander Alekseev
> <[email protected]> wrote:
> > > IMHO all files should be opened at least on startup to check
> > > integrity,
I would say s/startup/crash recovery/, if any.
> > That might be a lot of files to open.
>
> I was afraid of that, but let's say modern high-end is 200TB big DB,
> that's like 200*1024 1GB files, but I'm getting such time(1) timings
> for 204k files on ext4:
>
> $ time ./createfiles # real 0m2.157s, it's
> open(O_CREAT)+close()
> $ time ls -l many_files_dir/ > /dev/null # real 0m0.734s
> $ time ./openfiles # real 0m0.297s , for
> already existing ones (hot)
> $ time ./openfiles # real 0m1.456s , for
> already existing ones (cold, echo 3 > drop_caches sysctl)
>
> Not bad in my book as a one time activity. It could pose a problem
> potentially with some high latency open() calls, maybe NFS or
> something remote I guess.
Yeah, did you try on SAN as well? I am doubtful that will be performant.
Michael
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Subject: Re: The ability of postgres to determine loss of files of the main fork
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