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Date:      Thu, 16 Apr 2020 09:08:34 -0700 (PDT)
From:      "Rodney W. Grimes" <freebsd-rwg@gndrsh.dnsmgr.net>
To:        Wojciech Puchar <wojtek@puchar.net>
Cc:        freebsd-hackers@freebsd.org
Subject:   Re: fsck parallel check
Message-ID:  <202004161608.03GG8Ym1046249@gndrsh.dnsmgr.net>
In-Reply-To: <alpine.BSF.2.20.2004161748390.20589@puchar.net>

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> can it be changed?

It *could* be changed, but the more important question is *should*
it be changed.  See below.

> fsck checks in sequence all filesystems with 6-th field in /etc/fstab 
> equal 1, and in parallel all with 6-th field equal 2 but one process per 
> disk.
> 
> This is right if you have magnetic disks. checking 2 partitions in 
> parallel on one physical disk is bad idea.
> 
> But it is very good idea to do this on SSD with multiple partitions.

Why do you state that?

>From my perspective it is more that one thread is "good enough":
fsck should be I/O bound, more threads on a single ssd should just
lead to I/O queue building and no net reduction in time to complete.

Do you have some data that contridicts that?

> 
> Can it be changed ?

See above.

> 
> If not - i can write a fix for this (option settable in fstab).
-- 
Rod Grimes                                                 rgrimes@freebsd.org



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