Is there any place I can look for setting/getting infos about preferred
caching policies of external and/or network attached devices(storages). It
might not yet be available for
Win 2K !!!
-prokash
Never mind, it sounds like a dumb question !!!
I was looking for some programatic way to en(dis)albe write thru
caching for externally attached storage device. It seems like a
new thing for Xp, but might not be available for win 2k !!!
From msdn site I found some docs already…
thanks
–prokash
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Sinha, Prokash
Sent: Monday, January 26, 2004 11:46 AM
To: Windows System Software Devs Interest List
Subject: [ntdev] Peferred caching for external storage
Is there any place I can look for setting/getting infos about preferred
caching policies of external and/or network attached devices(storages). It
might not yet be available for
Win 2K !!!
-prokash
Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256
You are currently subscribed to ntdev as: xxxxx@garlic.com
To unsubscribe send a blank email to xxxxx@lists.osr.com
Writethrough behavior (so far limited to devices that support the SCSI-3
command sets, either SBC or RBC) is used for a purpose. Disabling or
blocking this except where storage has adequate battery backup is not
recommended. We have ample evidence that lack of writethrough on
non-RAID storage leads to data integrity problems. Some of that might be
due to bad drive behavior (such as dumping cache instead of committing
it when a device reset is seen or simply ignoring cache flush even on
IDE).
-----Original Message-----
From: Prokash Sinha [mailto:xxxxx@garlic.com]
Sent: Monday, January 26, 2004 7:43 PM
Subject: RE: Peferred caching for external storage
Never mind, it sounds like a dumb question !!!
I was looking for some programatic way to en(dis)albe write thru
caching for externally attached storage device. It seems like a
new thing for Xp, but might not be available for win 2k !!!
From msdn site I found some docs already…
thanks
–prokash
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Sinha, Prokash
Sent: Monday, January 26, 2004 11:46 AM
To: Windows System Software Devs Interest List
Subject: [ntdev] Peferred caching for external storage
Is there any place I can look for setting/getting infos about preferred
caching policies of external and/or network attached devices(storages).
It
might not yet be available for
Win 2K !!!
-prokash
Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256
You are currently subscribed to ntdev as: xxxxx@garlic.com
To unsubscribe send a blank email to xxxxx@lists.osr.com
Thanks Jeffery:
Is it still possible programmatically (on demand) to set this behavior
on/off ?
If so, is it only for XP ?
Also can I assume from your note that it is only available for SCSI-3 type
storage ?
I need to look at the doc today.
Thanks for your recommendation.
–prokash
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Jeffrey Goldner
Sent: Monday, January 26, 2004 10:22 PM
To: Windows System Software Devs Interest List
Subject: RE:[ntdev] Peferred caching for external storage
Writethrough behavior (so far limited to devices that support the SCSI-3
command sets, either SBC or RBC) is used for a purpose. Disabling or
blocking this except where storage has adequate battery backup is not
recommended. We have ample evidence that lack of writethrough on
non-RAID storage leads to data integrity problems. Some of that might be
due to bad drive behavior (such as dumping cache instead of committing
it when a device reset is seen or simply ignoring cache flush even on
IDE).
-----Original Message-----
From: Prokash Sinha [mailto:xxxxx@garlic.com]
Sent: Monday, January 26, 2004 7:43 PM
Subject: RE: Peferred caching for external storage
Never mind, it sounds like a dumb question !!!
I was looking for some programatic way to en(dis)albe write thru
caching for externally attached storage device. It seems like a
new thing for Xp, but might not be available for win 2k !!!
From msdn site I found some docs already…
thanks
–prokash
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Sinha, Prokash
Sent: Monday, January 26, 2004 11:46 AM
To: Windows System Software Devs Interest List
Subject: [ntdev] Peferred caching for external storage
Is there any place I can look for setting/getting infos about preferred
caching policies of external and/or network attached devices(storages).
It
might not yet be available for
Win 2K !!!
-prokash
Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256
You are currently subscribed to ntdev as: xxxxx@garlic.com
To unsubscribe send a blank email to xxxxx@lists.osr.com
Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256
You are currently subscribed to ntdev as: xxxxx@garlic.com
To unsubscribe send a blank email to xxxxx@lists.osr.com
I need to further understand if you are referring to the ability to turn
write caching on and off completely or you are specifically concerned
with FILE_FLAG_WRITE_THROUGH semantics. The former you can do if the
device supports either SCSI behavior (specifically mode page 8, WCE bit
can be changed) or the device is an IDE disk - we provide an IOCTL to do
this for you - see IOCTL_DISK_SET_CACHE_INFORMATION. Call
IOCTL_DISK_GET_CACHE_INFORMATION first to fill in the
DISK_CACHE_INFORMATION structure, then set WriteCacheEnabled to FALSE
and send it down with IOCTL_DISK_SET_CACHE_INFORMATION. Most RAID
controllers and subsystems don’t support this as cache settings are very
specific to the device and often involve more than a simple on/off
toggle.
-----Original Message-----
From: Prokash Sinha [mailto:xxxxx@garlic.com]
Sent: Tuesday, January 27, 2004 6:42 AM
Subject: RE: Peferred caching for external storage
Thanks Jeffery:
Is it still possible programmatically (on demand) to set this behavior
on/off ?
If so, is it only for XP ?
Also can I assume from your note that it is only available for SCSI-3
type
storage ?
I need to look at the doc today.
Thanks for your recommendation.
–prokash
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Jeffrey Goldner
Sent: Monday, January 26, 2004 10:22 PM
To: Windows System Software Devs Interest List
Subject: RE:[ntdev] Peferred caching for external storage
Writethrough behavior (so far limited to devices that support the SCSI-3
command sets, either SBC or RBC) is used for a purpose. Disabling or
blocking this except where storage has adequate battery backup is not
recommended. We have ample evidence that lack of writethrough on
non-RAID storage leads to data integrity problems. Some of that might be
due to bad drive behavior (such as dumping cache instead of committing
it when a device reset is seen or simply ignoring cache flush even on
IDE).
-----Original Message-----
From: Prokash Sinha [mailto:xxxxx@garlic.com]
Sent: Monday, January 26, 2004 7:43 PM
Subject: RE: Peferred caching for external storage
Never mind, it sounds like a dumb question !!!
I was looking for some programatic way to en(dis)albe write thru
caching for externally attached storage device. It seems like a
new thing for Xp, but might not be available for win 2k !!!
From msdn site I found some docs already…
thanks
–prokash
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Sinha, Prokash
Sent: Monday, January 26, 2004 11:46 AM
To: Windows System Software Devs Interest List
Subject: [ntdev] Peferred caching for external storage
Is there any place I can look for setting/getting infos about preferred
caching policies of external and/or network attached devices(storages).
It
might not yet be available for
Win 2K !!!
-prokash
Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256
You are currently subscribed to ntdev as: xxxxx@garlic.com
To unsubscribe send a blank email to xxxxx@lists.osr.com
Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256
You are currently subscribed to ntdev as: xxxxx@garlic.com
To unsubscribe send a blank email to xxxxx@lists.osr.com
I’m looking for a way to let an user know, if (s)he wants to have
the write-back or write-thru for external storage, both in the case of
RAID or non-RAID. As I see ( and of course I need to study more …) in the
doc that Xp’S surprise removal architecture for 1394, uSB, pcmcia and others
have
the ability to toggle this !!!. And sounds like, it is immaterial what is
underlying
storage protocols (SCCI-X, PATA, SATA …).
Thanks for all the info(s)…
-prokash
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Jeffrey Goldner
Sent: Tuesday, January 27, 2004 10:37 PM
To: Windows System Software Devs Interest List
Subject: RE:[ntdev] Peferred caching for external storage
I need to further understand if you are referring to the ability to turn
write caching on and off completely or you are specifically concerned
with FILE_FLAG_WRITE_THROUGH semantics. The former you can do if the
device supports either SCSI behavior (specifically mode page 8, WCE bit
can be changed) or the device is an IDE disk - we provide an IOCTL to do
this for you - see IOCTL_DISK_SET_CACHE_INFORMATION. Call
IOCTL_DISK_GET_CACHE_INFORMATION first to fill in the
DISK_CACHE_INFORMATION structure, then set WriteCacheEnabled to FALSE
and send it down with IOCTL_DISK_SET_CACHE_INFORMATION. Most RAID
controllers and subsystems don’t support this as cache settings are very
specific to the device and often involve more than a simple on/off
toggle.
-----Original Message-----
From: Prokash Sinha [mailto:xxxxx@garlic.com]
Sent: Tuesday, January 27, 2004 6:42 AM
Subject: RE: Peferred caching for external storage
Thanks Jeffery:
Is it still possible programmatically (on demand) to set this behavior
on/off ?
If so, is it only for XP ?
Also can I assume from your note that it is only available for SCSI-3
type
storage ?
I need to look at the doc today.
Thanks for your recommendation.
–prokash
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Jeffrey Goldner
Sent: Monday, January 26, 2004 10:22 PM
To: Windows System Software Devs Interest List
Subject: RE:[ntdev] Peferred caching for external storage
Writethrough behavior (so far limited to devices that support the SCSI-3
command sets, either SBC or RBC) is used for a purpose. Disabling or
blocking this except where storage has adequate battery backup is not
recommended. We have ample evidence that lack of writethrough on
non-RAID storage leads to data integrity problems. Some of that might be
due to bad drive behavior (such as dumping cache instead of committing
it when a device reset is seen or simply ignoring cache flush even on
IDE).
-----Original Message-----
From: Prokash Sinha [mailto:xxxxx@garlic.com]
Sent: Monday, January 26, 2004 7:43 PM
Subject: RE: Peferred caching for external storage
Never mind, it sounds like a dumb question !!!
I was looking for some programatic way to en(dis)albe write thru
caching for externally attached storage device. It seems like a
new thing for Xp, but might not be available for win 2k !!!
From msdn site I found some docs already…
thanks
–prokash
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Sinha, Prokash
Sent: Monday, January 26, 2004 11:46 AM
To: Windows System Software Devs Interest List
Subject: [ntdev] Peferred caching for external storage
Is there any place I can look for setting/getting infos about preferred
caching policies of external and/or network attached devices(storages).
It
might not yet be available for
Win 2K !!!
-prokash
Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256
You are currently subscribed to ntdev as: xxxxx@garlic.com
To unsubscribe send a blank email to xxxxx@lists.osr.com
Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256
You are currently subscribed to ntdev as: xxxxx@garlic.com
To unsubscribe send a blank email to xxxxx@lists.osr.com
Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256
You are currently subscribed to ntdev as: xxxxx@garlic.com
To unsubscribe send a blank email to xxxxx@lists.osr.com
The IOCTL information I provided below will tell you whether write
caching is enabled and allow you to turn it on or off. This will work on
ATA/SATA and individual disk drives using SCSI protocols including SCSI,
FC, SAS but usually not RAID subsystems or HBAs. It should also apply to
USB and 1394 but there is a lot of variation here, especially with
respect to USB. We make a default decision for most devices based on the
bus type and what the device itself can support - if we can get the
information from the device. If a device does not provide access to this
information in the standard locations (see
http://www.t10.org/ftp/t10/drafts/sbc/sbc-r08c.pdf or
http://www.t13.org/docs2003/d1532v1r3g.pdf for examples) there is
nothing the OS can do to toggle the state of the cache.
There is also no mechanism to distinguish between writeback and
writethrough implementations, although most caches on hard drives are
writeback. We’d like to see this in the future and will be proposing
something to the INCITS T10 committee.
-----Original Message-----
From: Prokash Sinha [mailto:xxxxx@garlic.com]
Sent: Wednesday, January 28, 2004 6:34 AM
Subject: RE: Peferred caching for external storage
I’m looking for a way to let an user know, if (s)he wants to have
the write-back or write-thru for external storage, both in the case of
RAID or non-RAID. As I see ( and of course I need to study more …) in
the
doc that Xp’S surprise removal architecture for 1394, uSB, pcmcia and
others
have
the ability to toggle this !!!. And sounds like, it is immaterial what
is
underlying
storage protocols (SCCI-X, PATA, SATA …).
Thanks for all the info(s)…
-prokash
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Jeffrey Goldner
Sent: Tuesday, January 27, 2004 10:37 PM
To: Windows System Software Devs Interest List
Subject: RE:[ntdev] Peferred caching for external storage
I need to further understand if you are referring to the ability to turn
write caching on and off completely or you are specifically concerned
with FILE_FLAG_WRITE_THROUGH semantics. The former you can do if the
device supports either SCSI behavior (specifically mode page 8, WCE bit
can be changed) or the device is an IDE disk - we provide an IOCTL to do
this for you - see IOCTL_DISK_SET_CACHE_INFORMATION. Call
IOCTL_DISK_GET_CACHE_INFORMATION first to fill in the
DISK_CACHE_INFORMATION structure, then set WriteCacheEnabled to FALSE
and send it down with IOCTL_DISK_SET_CACHE_INFORMATION. Most RAID
controllers and subsystems don’t support this as cache settings are very
specific to the device and often involve more than a simple on/off
toggle.
-----Original Message-----
From: Prokash Sinha [mailto:xxxxx@garlic.com]
Sent: Tuesday, January 27, 2004 6:42 AM
Subject: RE: Peferred caching for external storage
Thanks Jeffery:
Is it still possible programmatically (on demand) to set this behavior
on/off ?
If so, is it only for XP ?
Also can I assume from your note that it is only available for SCSI-3
type
storage ?
I need to look at the doc today.
Thanks for your recommendation.
–prokash
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Jeffrey Goldner
Sent: Monday, January 26, 2004 10:22 PM
To: Windows System Software Devs Interest List
Subject: RE:[ntdev] Peferred caching for external storage
Writethrough behavior (so far limited to devices that support the SCSI-3
command sets, either SBC or RBC) is used for a purpose. Disabling or
blocking this except where storage has adequate battery backup is not
recommended. We have ample evidence that lack of writethrough on
non-RAID storage leads to data integrity problems. Some of that might be
due to bad drive behavior (such as dumping cache instead of committing
it when a device reset is seen or simply ignoring cache flush even on
IDE).
-----Original Message-----
From: Prokash Sinha [mailto:xxxxx@garlic.com]
Sent: Monday, January 26, 2004 7:43 PM
Subject: RE: Peferred caching for external storage
Never mind, it sounds like a dumb question !!!
I was looking for some programatic way to en(dis)albe write thru
caching for externally attached storage device. It seems like a
new thing for Xp, but might not be available for win 2k !!!
From msdn site I found some docs already…
thanks
–prokash
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Sinha, Prokash
Sent: Monday, January 26, 2004 11:46 AM
To: Windows System Software Devs Interest List
Subject: [ntdev] Peferred caching for external storage
Is there any place I can look for setting/getting infos about preferred
caching policies of external and/or network attached devices(storages).
It
might not yet be available for
Win 2K !!!
-prokash
Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256
You are currently subscribed to ntdev as: xxxxx@garlic.com
To unsubscribe send a blank email to xxxxx@lists.osr.com
Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256
You are currently subscribed to ntdev as: xxxxx@garlic.com
To unsubscribe send a blank email to xxxxx@lists.osr.com
Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256
You are currently subscribed to ntdev as: xxxxx@garlic.com
To unsubscribe send a blank email to xxxxx@lists.osr.com
Jeffrey:
Now I got it.
Much appreciated.
Thanks a bunch.
-prokash
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Jeffrey Goldner
Sent: Wednesday, January 28, 2004 9:27 PM
To: Windows System Software Devs Interest List
Subject: RE:[ntdev] Peferred caching for external storage
The IOCTL information I provided below will tell you whether write
caching is enabled and allow you to turn it on or off. This will work on
ATA/SATA and individual disk drives using SCSI protocols including SCSI,
FC, SAS but usually not RAID subsystems or HBAs. It should also apply to
USB and 1394 but there is a lot of variation here, especially with
respect to USB. We make a default decision for most devices based on the
bus type and what the device itself can support - if we can get the
information from the device. If a device does not provide access to this
information in the standard locations (see
http://www.t10.org/ftp/t10/drafts/sbc/sbc-r08c.pdf or
http://www.t13.org/docs2003/d1532v1r3g.pdf for examples) there is
nothing the OS can do to toggle the state of the cache.
There is also no mechanism to distinguish between writeback and
writethrough implementations, although most caches on hard drives are
writeback. We’d like to see this in the future and will be proposing
something to the INCITS T10 committee.
-----Original Message-----
From: Prokash Sinha [mailto:xxxxx@garlic.com]
Sent: Wednesday, January 28, 2004 6:34 AM
Subject: RE: Peferred caching for external storage
I’m looking for a way to let an user know, if (s)he wants to have
the write-back or write-thru for external storage, both in the case of
RAID or non-RAID. As I see ( and of course I need to study more …) in
the
doc that Xp’S surprise removal architecture for 1394, uSB, pcmcia and
others
have
the ability to toggle this !!!. And sounds like, it is immaterial what
is
underlying
storage protocols (SCCI-X, PATA, SATA …).
Thanks for all the info(s)…
-prokash
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Jeffrey Goldner
Sent: Tuesday, January 27, 2004 10:37 PM
To: Windows System Software Devs Interest List
Subject: RE:[ntdev] Peferred caching for external storage
I need to further understand if you are referring to the ability to turn
write caching on and off completely or you are specifically concerned
with FILE_FLAG_WRITE_THROUGH semantics. The former you can do if the
device supports either SCSI behavior (specifically mode page 8, WCE bit
can be changed) or the device is an IDE disk - we provide an IOCTL to do
this for you - see IOCTL_DISK_SET_CACHE_INFORMATION. Call
IOCTL_DISK_GET_CACHE_INFORMATION first to fill in the
DISK_CACHE_INFORMATION structure, then set WriteCacheEnabled to FALSE
and send it down with IOCTL_DISK_SET_CACHE_INFORMATION. Most RAID
controllers and subsystems don’t support this as cache settings are very
specific to the device and often involve more than a simple on/off
toggle.
-----Original Message-----
From: Prokash Sinha [mailto:xxxxx@garlic.com]
Sent: Tuesday, January 27, 2004 6:42 AM
Subject: RE: Peferred caching for external storage
Thanks Jeffery:
Is it still possible programmatically (on demand) to set this behavior
on/off ?
If so, is it only for XP ?
Also can I assume from your note that it is only available for SCSI-3
type
storage ?
I need to look at the doc today.
Thanks for your recommendation.
–prokash
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Jeffrey Goldner
Sent: Monday, January 26, 2004 10:22 PM
To: Windows System Software Devs Interest List
Subject: RE:[ntdev] Peferred caching for external storage
Writethrough behavior (so far limited to devices that support the SCSI-3
command sets, either SBC or RBC) is used for a purpose. Disabling or
blocking this except where storage has adequate battery backup is not
recommended. We have ample evidence that lack of writethrough on
non-RAID storage leads to data integrity problems. Some of that might be
due to bad drive behavior (such as dumping cache instead of committing
it when a device reset is seen or simply ignoring cache flush even on
IDE).
-----Original Message-----
From: Prokash Sinha [mailto:xxxxx@garlic.com]
Sent: Monday, January 26, 2004 7:43 PM
Subject: RE: Peferred caching for external storage
Never mind, it sounds like a dumb question !!!
I was looking for some programatic way to en(dis)albe write thru
caching for externally attached storage device. It seems like a
new thing for Xp, but might not be available for win 2k !!!
From msdn site I found some docs already…
thanks
–prokash
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Sinha, Prokash
Sent: Monday, January 26, 2004 11:46 AM
To: Windows System Software Devs Interest List
Subject: [ntdev] Peferred caching for external storage
Is there any place I can look for setting/getting infos about preferred
caching policies of external and/or network attached devices(storages).
It
might not yet be available for
Win 2K !!!
-prokash
Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256
You are currently subscribed to ntdev as: xxxxx@garlic.com
To unsubscribe send a blank email to xxxxx@lists.osr.com
Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256
You are currently subscribed to ntdev as: xxxxx@garlic.com
To unsubscribe send a blank email to xxxxx@lists.osr.com
Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256
You are currently subscribed to ntdev as: xxxxx@garlic.com
To unsubscribe send a blank email to xxxxx@lists.osr.com
Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256
You are currently subscribed to ntdev as: xxxxx@garlic.com
To unsubscribe send a blank email to xxxxx@lists.osr.com