From: Killian De Volder <killian.de.volder@megasoft.be>
To: linux-bcache@vger.kernel.org
Subject: Re: Cache everything
Date: Fri, 30 Dec 2016 09:58:19 +0100 [thread overview]
Message-ID: <586621AB.7040208@megasoft.be> (raw)
In-Reply-To: <CAJ=9zif=Lxgcgv0EW8O7hfKDHn5g8acXKnbvygda6LjarL65Xg@mail.gmail.com>
Also check congested_write_threshold_us, if the SSD is "congested" it bypasses it to speedup writes.
Killian De Volder
On 30-12-16 09:38, Jure Erznožnik wrote:
> I have a large array sitting in my server containing a bit of data
> that is used ofter and a lot of data that is used rarely.
> My goal is to make the platters spin up as rarely as possible while
> bcache handles most of the requests to the array.
>
> I have set the disks spin-down time to 15 minutes so that during
> high-activity periods they don't cycle power states too much.
>
> I have set bcache parameters such:
> cache_mode - writeback
> readahead - 0
> sequential_cutoff - 0
> writeback_delay - 3600 (one hour)
> writeback_percent - 40 (won't go higher)
>
> I was hoping that this would make bcache cache everything leaving the
> array practically untouched for an hour. However, stats_hour/bypassed
> still shows megabytes of bypassed data and a cache_hit ratio of ~50%
> even when I'm working ONLY with the frequently accessed data portion
> (some 20% of total cache capacity). Also tiny writes are being made to
> the array despite writeback_delay not expiring.
>
> What other parameter am I forgetting to achieve what I want?
>
> Thanks,
> Jure
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next prev parent reply other threads:[~2016-12-30 8:58 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-30 8:38 Cache everything Jure Erznožnik
2016-12-30 8:58 ` Killian De Volder [this message]
2016-12-31 5:20 ` Jure Erznožnik
2017-01-30 10:31 ` Jure Erznožnik
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