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Date:      Fri, 29 Nov 2013 20:35:20 -0000
From:      "Steven Hartland" <killing@multiplay.co.uk>
To:        <krichy@cflinux.hu>, <freebsd-scsi@freebsd.org>
Subject:   Re: Fwd: Re: ssd for zfs
Message-ID:  <EA212CF8655D4EA6BD6AF9019470E5DE@multiplay.co.uk>
References:  <0b12c19b8832c72369ff7244d7231846@cflinux.hu> <81b87ca49aef7d88db1b4dbd5f7eb201@cflinux.hu> <923bc6b4aa9141e5e9a49ab76b3a18b5@cflinux.hu>

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You could add a DA_Q_NO_SYNC_CACHE quirk for you device
which will prevent the cam layer attempting to call sync but this
will only work if its attached to a SCSI controller like an LSI there's
no such quirk currently implemented in ATA cam layer.

    Regards
    Steve
----- Original Message ----- 
From: <krichy@cflinux.hu>
To: <freebsd-scsi@freebsd.org>
Sent: Friday, November 29, 2013 8:17 PM
Subject: Re: Fwd: Re: ssd for zfs


> Dear scsi-devs,
> 
> It seems that my device handles the flush commands slowly. The linux 
> code avoids issuing this if the device reports its write cache is turned 
> off. That way my SSD works fast under linux, but infortunately slow 
> under FreeBSD. Actually I dont understand why is it slow for the flush 
> command, as it has power-loss-protection, maybe for such a command it 
> really flushes everything out, dont know. But when I enable the write 
> cache in linux also, the block layer gets knowledge of the write cache, 
> it issues the flush commands, and it gets same slow.
> 
> How could this be solved?


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