[Bug 13499] Write cache: disabled, read cache: enabled, supports DPO and FUA? it's bug???

[Bug 13499] Write cache: disabled, read cache: enabled, supports DPO and FUA? it's bug???

[bugzilla-daemon]

http://bugzilla.kernel.org/show_bug.cgi?id=13499





--- Comment #1 from ping.li <lxy9805287@163.com>  2009-06-10 14:00:53 ---
Write cache: disabled, read cache: enabled,


why Write cache: disabled??

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Re: [Bug 13499] Write cache: disabled, read cache: enabled, supports DPO and FUA? it's bug???

[James Bottomley]

On Wed, 2009-06-10 at 14:00 +0000, bugzilla-daemon@bugzilla.kernel.org
wrote:
> why Write cache: disabled??

The SCSI mid layer is merely reporting what your array is telling it.
For arrays without a battery backed cache, write through configuration
(i.e. read cache enabled, write cache disabled) is the usual safe
default.

You can alter your write cache settings using Doug Gilbert's
sg3-utils ... but be warned, enabling the write cache without battery
backing in an array is a dangerous thing to do since most arrays have
huge caches, they either ignore SYNCHRONIZE CACHE (which would leave you
vulnerable to data loss on power failure) or take such a long time, it
would kill performance.

James

[Bug 13499] Write cache: disabled, read cache: enabled, supports DPO and FUA? it's bug???

[bugzilla-daemon]

http://bugzilla.kernel.org/show_bug.cgi?id=13499





--- Comment #2 from Anonymous Emailer <anonymous@kernel-bugs.osdl.org>  2009-06-10 14:14:13 ---
Reply-To: James.Bottomley@HansenPartnership.com

On Wed, 2009-06-10 at 14:00 +0000, bugzilla-daemon@bugzilla.kernel.org
wrote:
> why Write cache: disabled??

The SCSI mid layer is merely reporting what your array is telling it.
For arrays without a battery backed cache, write through configuration
(i.e. read cache enabled, write cache disabled) is the usual safe
default.

You can alter your write cache settings using Doug Gilbert's
sg3-utils ... but be warned, enabling the write cache without battery
backing in an array is a dangerous thing to do since most arrays have
huge caches, they either ignore SYNCHRONIZE CACHE (which would leave you
vulnerable to data loss on power failure) or take such a long time, it
would kill performance.

James

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[Bug 13499] Write cache: disabled, read cache: enabled, supports DPO and FUA? it's bug???

[bugzilla-daemon]

http://bugzilla.kernel.org/show_bug.cgi?id=13499





--- Comment #3 from ping.li <lxy9805287@163.com>  2009-06-10 17:04:29 ---
1. BBU  status is ok
./MegaCli64 -AdpBbuCmd -GetBbuStatus -a0

BBU status for Adapter: 0

BatteryType: BBU
Voltage: 4058 mV
Current: 0 mA
Temperature: 19 C
Firmware Status: 00000000

Battery state:

GasGuageStatus:
  Fully Discharged        : No
  Fully Charged           : Yes
  Discharging             : Yes
  Initialized             : Yes
  Remaining Time Alarm    : No
  Remaining Capacity Alarm: No
  Discharge Terminated    : No
  Over Temperature        : No
  Charging Terminated     : Yes
  Over Charged            : No

Relative State of Charge: 98 %
Charger Status: Complete
Remaining Capacity: 1634 mAh
Full Charge Capacity: 1662 mAh
isSOHGood: Yes

2. Cache Policy is default,and try change setting but problem still.

./MegaCli64 -LDinfo -L0 -a0
Adapter 0 -- Virtual Drive Information:
Virtual Disk: 0 (target id: 0)
Name:
RAID Level: Primary-5, Secondary-0, RAID Level Qualifier-3
Size:975744MB
State: Optimal
Stripe Size: 64kB
Number Of Drives:8
Span Depth:1
Default Cache Policy: WriteBack, ReadAheadNone, Direct, Write Cache OK if Bad
BBU
Current Cache Policy: WriteBack, ReadAheadNone, Direct, Write Cache OK if Bad
BBU
Access Policy: Read/Write
Disk Cache Policy: Enabled

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[Bug 13499] Write cache: disabled, read cache: enabled, supports DPO and FUA? it's bug???

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=13499


Alan <alan@lxorguk.ukuu.org.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |alan@lxorguk.ukuu.org.uk
         Resolution|                            |OBSOLETE




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[Bug 13499] Write cache: disabled, read cache: enabled, supports DPO and FUA? it's bug???

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=13499


Alan <alan@lxorguk.ukuu.org.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |CLOSED




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