On Wed, 2013-04-24 at 05:44 +, Elliott, Robert (Server Storage)
wrote:
> If the writeback cache is enabled (per the WCE bit in the Caching mode page),
> prudent software uses the FUA bit in WRITE commands when writing metadata
> and/or sends the SYNCHRONIZE CACHE command at important checkpoint
Il 25/04/2013 03:32, Martin K. Petersen ha scritto:
> I'm ok with your patch. And a strong believer in not altering the
> SYNCHRONIZE CACHE behavior that's been rigorously tested in the field by
> adding SYNC_NV to the mix.
SYNC_NV is absolutely necessary for targets that (a) have both volatile
an
On Thu, 2013-04-25 at 07:35 -0400, Ric Wheeler wrote:
> It was pointed out to me that RCD is "Read Cache Disable" so by
> setting it to
> zero, we are enabling the read cache (not that we ever look at this
> bit or send
> it down). The WCE bit is "write cache enable" so the polarity of the
> bits
On 04/24/2013 06:46 PM, James Bottomley wrote:
On Wed, 2013-04-24 at 18:36 -0400, Ric Wheeler wrote:
On 04/24/2013 06:09 PM, James Bottomley wrote:
On Wed, 2013-04-24 at 23:54 +0200, Paolo Bonzini wrote:
Il 24/04/2013 23:02, James Bottomley ha scritto:
That just leaves us with random standard
> "James" == James Bottomley writes:
James> I'm fairly ambivalent, except not force. The default behaviour
James> is to do the mode select, so force seems to imply that as well,
James> except it won't. I don't see a difference between assume and
James> temporary.
I'm ok with your patch. An
On Wed, 2013-04-24 at 18:36 -0400, Ric Wheeler wrote:
> On 04/24/2013 06:09 PM, James Bottomley wrote:
> > On Wed, 2013-04-24 at 23:54 +0200, Paolo Bonzini wrote:
> >> Il 24/04/2013 23:02, James Bottomley ha scritto:
> >>> That just leaves us with random standards behaviour. Lets permit the
> >>>
On 04/24/2013 06:09 PM, James Bottomley wrote:
On Wed, 2013-04-24 at 23:54 +0200, Paolo Bonzini wrote:
Il 24/04/2013 23:02, James Bottomley ha scritto:
That just leaves us with random standards behaviour. Lets permit the
deterministic thing instead for the distros. It kills two birds with
one
On Wed, 2013-04-24 at 23:54 +0200, Paolo Bonzini wrote:
> Il 24/04/2013 23:02, James Bottomley ha scritto:
> > That just leaves us with random standards behaviour. Lets permit the
> > deterministic thing instead for the distros. It kills two birds with
> > one stone because we can set WCE for the
Il 24/04/2013 23:02, James Bottomley ha scritto:
> That just leaves us with random standards behaviour. Lets permit the
> deterministic thing instead for the distros. It kills two birds with
> one stone because we can set WCE for the stupid UAS devices that clear
> it wrongly as well.
>
> For th
On Wed, 2013-04-24 at 16:41 -0400, Ric Wheeler wrote:
> On 04/24/2013 02:20 PM, Black, David wrote:
> > Jeremy,
> >
> > It looks like, you, Paolo and Ric have hit the nail on the head here - this
> > is
> > a nice summary, IMHO:
> >
> >> On 4/24/2013 7:57 AM, Paolo Bonzini wrote:
> If the dev
On 04/24/2013 02:20 PM, Black, David wrote:
Jeremy,
It looks like, you, Paolo and Ric have hit the nail on the head here - this is
a nice summary, IMHO:
On 4/24/2013 7:57 AM, Paolo Bonzini wrote:
If the device can promise this, we don't care (and don't know) how it
manages that promise. It ca
ginal Message-
> From: Jeremy Linton [mailto:jlin...@tributary.com]
> Sent: Wednesday, April 24, 2013 10:36 AM
> To: Paolo Bonzini
> Cc: Ric Wheeler; Hannes Reinecke; James Bottomley; linux-scsi@vger.kernel.org;
> Martin K. Petersen; Jeff Moyer; Tejun Heo; Mike Snitzer; Black, David;
&g
On 13-04-23 03:41 PM, Ric Wheeler wrote:
For many years, we have used WCE as an indication that a device has a volatile
write cache (not just a write cache) and used this as a trigger to send down
SYNCHRONIZE_CACHE commands as needed.
Some arrays with non-volatile cache seem to have WCE set and
On 4/24/2013 7:57 AM, Paolo Bonzini wrote:
>> If the device can promise this, we don't care (and don't know) how it
>> manages that promise. It can leave the data on battery backed DRAM, can
>> archive it to flash or any other scheme that works.
>
> That's exactly the point of SYNC_NV=1.
Il 24/04/2013 14:27, Ric Wheeler ha scritto:
>> The point is to _avoid_ hitting the disk. :)
>
> The point is to have a crash-proof version of the data acknowledged by
> the target device while letting data sit in volatile state as long as
> possible. To be even clearer, we would love to do this f
On 04/24/2013 08:08 AM, Paolo Bonzini wrote:
Il 24/04/2013 14:07, Hannes Reinecke ha scritto:
On 04/24/2013 01:17 PM, Paolo Bonzini wrote:
Il 23/04/2013 22:07, James Bottomley ha scritto:
On Tue, 2013-04-23 at 15:41 -0400, Ric Wheeler wrote:
For many years, we have used WCE as an indication t
On Wed, Apr 24 2013 at 8:12am -0400,
Hannes Reinecke wrote:
> On 04/24/2013 02:08 PM, Paolo Bonzini wrote:
> > Il 24/04/2013 14:07, Hannes Reinecke ha scritto:
> >> On 04/24/2013 01:17 PM, Paolo Bonzini wrote:
> >>> Il 23/04/2013 22:07, James Bottomley ha scritto:
> On Tue, 2013-04-23 at 15
Il 24/04/2013 14:12, Hannes Reinecke ha scritto:
> On 04/24/2013 02:08 PM, Paolo Bonzini wrote:
>> Il 24/04/2013 14:07, Hannes Reinecke ha scritto:
>>> On 04/24/2013 01:17 PM, Paolo Bonzini wrote:
Il 23/04/2013 22:07, James Bottomley ha scritto:
> On Tue, 2013-04-23 at 15:41 -0400, Ric Whe
On 04/24/2013 02:08 PM, Paolo Bonzini wrote:
> Il 24/04/2013 14:07, Hannes Reinecke ha scritto:
>> On 04/24/2013 01:17 PM, Paolo Bonzini wrote:
>>> Il 23/04/2013 22:07, James Bottomley ha scritto:
On Tue, 2013-04-23 at 15:41 -0400, Ric Wheeler wrote:
> For many years, we have used WCE as a
Il 24/04/2013 14:07, Hannes Reinecke ha scritto:
> On 04/24/2013 01:17 PM, Paolo Bonzini wrote:
>> Il 23/04/2013 22:07, James Bottomley ha scritto:
>>> On Tue, 2013-04-23 at 15:41 -0400, Ric Wheeler wrote:
For many years, we have used WCE as an indication that a device has a
volatile
>>
On 04/24/2013 01:17 PM, Paolo Bonzini wrote:
> Il 23/04/2013 22:07, James Bottomley ha scritto:
>> On Tue, 2013-04-23 at 15:41 -0400, Ric Wheeler wrote:
>>> For many years, we have used WCE as an indication that a device has a
>>> volatile
>>> write cache (not just a write cache) and used this as
On 04/23/2013 10:07 PM, James Bottomley wrote:
> On Tue, 2013-04-23 at 15:41 -0400, Ric Wheeler wrote:
>> For many years, we have used WCE as an indication that a device has a
>> volatile
>> write cache (not just a write cache) and used this as a trigger to send down
>> SYNCHRONIZE_CACHE command
Il 23/04/2013 22:07, James Bottomley ha scritto:
> On Tue, 2013-04-23 at 15:41 -0400, Ric Wheeler wrote:
>> For many years, we have used WCE as an indication that a device has a
>> volatile
>> write cache (not just a write cache) and used this as a trigger to send down
>> SYNCHRONIZE_CACHE comma
ey
Cc: Ric Wheeler; linux-scsi@vger.kernel.org; Martin K. Petersen; Jeff Moyer;
Tejun Heo; Mike Snitzer; dgilb...@interlog.com
Subject: Re: T10 WCE interpretation in Linux & device level access
On 4/23/2013 3:07 PM, James Bottomley wrote:
I bet they don't; they probably obey the spec. Th
ux-scsi-ow...@vger.kernel.org] On Behalf Of Jeremy Linton
Sent: Tuesday, April 23, 2013 5:40 PM
To: James Bottomley
Cc: Ric Wheeler; linux-scsi@vger.kernel.org; Martin K. Petersen; Jeff Moyer;
Tejun Heo; Mike Snitzer; dgilb...@interlog.com
Subject: Re: T10 WCE interpretation in Linux & device level a
On 4/23/2013 3:07 PM, James Bottomley wrote:
>
> I bet they don't; they probably obey the spec. There's a SYNC_NV bit
> which if unset (which it is in our implementation) means only sync your
> non-NV cache. For a device with all NV, that equates to nop.
Yes, linux leaves the SYNC_NV b
On 13-04-23 03:41 PM, Ric Wheeler wrote:
For many years, we have used WCE as an indication that a device has a volatile
write cache (not just a write cache) and used this as a trigger to send down
SYNCHRONIZE_CACHE commands as needed.
Some arrays with non-volatile cache seem to have WCE set and
On Tue, 2013-04-23 at 15:41 -0400, Ric Wheeler wrote:
> For many years, we have used WCE as an indication that a device has a
> volatile
> write cache (not just a write cache) and used this as a trigger to send down
> SYNCHRONIZE_CACHE commands as needed.
>
> Some arrays with non-volatile cache
For many years, we have used WCE as an indication that a device has a volatile
write cache (not just a write cache) and used this as a trigger to send down
SYNCHRONIZE_CACHE commands as needed.
Some arrays with non-volatile cache seem to have WCE set and simply ignore the
command.
Some arr
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