Re: [pbs-devel] [PATCH proxmox 2/2] pbs api types: add option to set GC chunk cleanup wait period

From: "Fabian Grünbichler" <f.gruenbichler@proxmox.com>
To: Christian Ebner <c.ebner@proxmox.com>,
	Proxmox Backup Server development discussion
	<pbs-devel@lists.proxmox.com>,
	Thomas Lamprecht <t.lamprecht@proxmox.com>
Subject: Re: [pbs-devel] [PATCH proxmox 2/2] pbs api types: add option to set GC chunk cleanup wait period
Date: Wed, 05 Mar 2025 09:12:13 +0100	[thread overview]
Message-ID: <1741161467.n7xtjkjof1.astroid@yuna.none> (raw)
In-Reply-To: <7c0d6e54-1f71-4c05-b4f6-00779b8d2673@proxmox.com>

On March 4, 2025 5:49 pm, Thomas Lamprecht wrote:
> Am 04.03.25 um 17:37 schrieb Christian Ebner:
>> On 3/4/25 17:01, Thomas Lamprecht wrote:
>>> Would be fine by me to reducing the minimum to zero. And the extra 5
>>> minutes are "just to be sure" safety-margin, not a requirement for
>>> anything IIRC.
>> 
>> Discussed this with Fabian rather extensively today. Only reason to keep 
>> a small safety margin here is for small time drift in case of remote 
>> storages (if they use their local time for timestamps).
> 
> Ah, you mean network attached remote storage, but while your reasons
> below are fine, doing this for time drifts is IMO not really strong
> argumentation, as if one allows for no time synchronisation then there
> won't be a limit to the drift amount, but ...

actually, the translation from UTIME_NOW to timestamp happens in the
local kernel, so time drift shouldn't matter much here..

>> But this can be much lower, would opt for 1 minute to stay within the 
>> minute range.
>> 
>> Also, atime always uses the coarse resolution for timestamp updates, 
>> that will also not change with the multi-grained timestamp resolutions 
>> in https://origin.kernel.org/doc/html/v6.13/filesystems/multigrain-ts.html
>> So this has to be taken into account for the atime update check, and 
>> since setting the atime into the past will introduce other error modes 
>> (permissions, fs impl, ...), a short wait of a 1 second in-between must 
>> be used.
>> 
>> Also, there is no distinction to be made between filesystems mounted 
>> with atime and relatime, if the explicit atime update fails, the GC 
> 
> ... this actually is a strong argument, so I'm fine with a Minute as
> minimum.

but this is still a valid reason to leave a small buffer :)

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