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In-Reply-To: <0f5aafed-7b1a-99ac-57fc-c5de9a269b92@youngman.org.uk>
From:   Roger Heflin <rogerheflin@gmail.com>
Date:   Wed, 15 Feb 2023 09:22:33 -0600
Message-ID: <CAAMCDed2eaygbYxFWDMBKELJ27XKNUZgGsJ1MKQK8qMCUTy+wA@mail.gmail.com>
Subject: Re: [dm-devel] RAID4 with no striping mode request
To:     Wols Lists <antlists@youngman.org.uk>
Cc:     Heinz Mauelshagen <heinzm@redhat.com>,
        Kyle Sanderson <kyle.leet@gmail.com>,
        linux-raid@vger.kernel.org, Song Liu <song@kernel.org>,
        device-mapper development <dm-devel@redhat.com>,
        John Stoffel <john@stoffel.org>,
        Linux-Kernel <linux-kernel@vger.kernel.org>
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Precedence: bulk

The SMART on the disk marks the disk as FAILED when you hit the
manufacturer's posted limit (1000 or 2000 writes average).    I am
sure using a "FAILED" disk would make a lot of people nervous.

The conclusion of you can write as fast as you can and it will take 3
years to wear out would be specific to that specific brand/version
with a given set of chips in it, and may or may not hold to other
vendors/chips/versions, and so may have quite a bit of variation in
it.  I think I remember seeing that, but I don't remember what the
average write rate was.  The one I just found says 200TB of writes on
a 240g drive, so about 8000erases per cell was the lowest failure
rate, with some drives making it 3-5x higher.


On Wed, Feb 15, 2023 at 8:53 AM Wols Lists <antlists@youngman.org.uk> wrote:
>
> On 15/02/2023 11:44, Roger Heflin wrote:
> > WOL: current SSD's are rated for around 1000-2000 writes.  So a 1Tb
> > disk can sustain 1000-2000TB of total writes.  And writes to
> > filesystem blocks would get re-written more often than data blocks.
> >   How well it would work would depend on how often the data is deleted
> > and re-written.
>
> When did that guy do that study of SSDs? Basically hammered them to
> death 24/7? I think it took about three years of continuous write/erase
> cycles to destroy them.
>
> Given that most drives are obsolete long before they've had three years
> of writes ... the conclusion was that - for the same write load -
> "modern" (as they were several years ago) SSDs would probably outlast
> mechanical drives for the same workload.
>
> (Cheap SD cards, on the other hand ...)
>
> Cheers,
> Wol