Re: SATA kernel-buffered read VERY slow (not raid, Promise TX300 card); 2.6.23.1(vanilla)

Re: SATA kernel-buffered read VERY slow (not raid, Promise TX300 card); 2.6.23.1(vanilla)

[Robert Hancock]

Linda Walsh wrote:
> Robert Hancock wrote:
>> Linda Walsh wrote:
>>> Alan Cox wrote:
>>>>> rate began falling; at 128k block-reads-at-a-time or larger, it 
>>>>> drops below
>>>>> 20MB/s (only on buffered SATA).
>>>> Try disabling NCQ - see if you've got a drive with the 'NCQ = no
>>>> readahead' flaw.
>> http://linux-ata.org/faq.html#ncq
> ---
>    When drive initializes, dmesg says it has NCQ (depth 0/32)
>    Reading the queue_depth under /sys, shows a queuedepth of "1".

Looks like your controller (or at least the Linux driver) doesn't 
actually support NCQ.

>>> 2) Drive Advanced Power Management setting("-B") (write-only):
>>> "HDIO_DRIVE_CMD failed: Input/output error"
>>> 3) Drive Acoustic ("-M"), read = " acoustic      = not supported",
>>> write = " HDIO_DRIVE_CMD:ACOUSTIC failed: Input/output error"
>>
>> Not sure about these ones.. Does anything show up in dmesg when you do 
>> this?
> ---
>    Yes:
>    (for "-B", power-management)
> ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x0
> ata1.00: port_status 0x20200000
> ata1.00: cmd ef/05:fe:00:00:00/00:00:00:00:00/40 tag 0 cdb 0x0 data 0
>         res 51/04:fe:00:00:00/00:00:00:00:00/40 Emask 0x1 (device error)
> ata1.00: configured for UDMA/133
> ata1: EH complete
> sd 1:0:0:0: [sdb] 1465149168 512-byte hardware sectors (750156 MB)
> sd 1:0:0:0: [sdb] Write Protect is off
> sd 1:0:0:0: [sdb] Mode Sense: 00 3a 00 00
> sd 1:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't 
> support DPO or FUA
> ----
>   (for "-M" acoustic management):
> ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x0
> ata1.00: port_status 0x20200000
> ata1.00: cmd ef/42:fe:00:00:00/00:00:00:00:00/40 tag 0 cdb 0x0 data 0
>         res 51/04:fe:00:00:00/00:00:00:00:00/40 Emask 0x1 (device error)
> ata1.00: configured for UDMA/133
> ata1: EH complete
> sd 1:0:0:0: [sdb] 1465149168 512-byte hardware sectors (750156 MB)
> sd 1:0:0:0: [sdb] Write Protect is off
> sd 1:0:0:0: [sdb] Mode Sense: 00 3a 00 00
> sd 1:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't 
> support DPO or FUA

Looks like the drive reports ERR/ABRT (command aborted), meaning it 
likely doesn't support those commands.

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/

Re: SATA kernel-buffered read VERY slow (not raid, Promise TX300 card); 2.6.23.1(vanilla)

[Linda Walsh]

Robert Hancock wrote:
>
> Looks like the drive reports ERR/ABRT (command aborted), meaning it 
> likely doesn't support those commands.
>
---
    Except the PATA version of the drive does (same capacity, & other 
specs).  Seagate would
disable "advanced" features for SATA but leave them for the older 
technology?  Possible,
but doesn't seem likely.

Re: SATA kernel-buffered read VERY slow (not raid, Promise TX300 card); 2.6.23.1(vanilla)

[Robert Hancock]

Linda Walsh wrote:
> Robert Hancock wrote:
>>
>> Looks like the drive reports ERR/ABRT (command aborted), meaning it 
>> likely doesn't support those commands.
>>
> ---
>    Except the PATA version of the drive does (same capacity, & other 
> specs).  Seagate would
> disable "advanced" features for SATA but leave them for the older 
> technology?  Possible,
> but doesn't seem likely.

If this is a Seagate, I believe that they don't have AAM enabled on any 
of their newer drives (something about a lawsuit for patent infringement 
on that feature, or something). Quite likely they don't support that 
power management command, either.

Re: SATA kernel-buffered read VERY slow (not raid, Promise TX300 card); 2.6.23.1(vanilla)

[Linda Walsh]

Robert Hancock wrote:
>
> If this is a Seagate, I believe that they don't have AAM enabled on 
> any of their newer drives (something about a lawsuit for patent 
> infringement on that feature, or something). Quite likely they don't 
> support that power management command, either.
--
    Do you have a source for this -- haven't heard of such a conflict -- 
besides, doesn't
ATA-7 require some of those functions?  Given the trend toward 
power-saving and
quieter (also usually less vibration)  hard disks, I strongly disbelieve 
Seagate would
remove those features -- especially since they are mentioned on 
Seagate's drive
information page as being supported features.

Re: SATA kernel-buffered read VERY slow (not raid, Promise TX300 card); 2.6.23.1(vanilla)

[Mehmet Kemal EROL]

Linda Walsh:

> 
> Seagate would
> remove those features -- especially since they are mentioned on 
> Seagate's drive
> information page as being supported features.
> 

Since you're there ... you might want to download `Seagate's SeaTools'
and (if) give the hdd's controller a try ... ;)

-- 
Esenlikle   <~>   Mehmet Kemal

_/_/  IBM Pollyanna Principle:
_/    Machines should work,
_/    People should think...

Re: SATA kernel-buffered read VERY slow (not raid, Promise TX300 card); 2.6.23.1(vanilla)

[Alan Cox]

On Sun, 06 Jan 2008 12:25:10 -0800
Linda Walsh <lkml@tlinx.org> wrote:

> Robert Hancock wrote:
> >
> > If this is a Seagate, I believe that they don't have AAM enabled on 
> > any of their newer drives (something about a lawsuit for patent 
> > infringement on that feature, or something). Quite likely they don't 
> > support that power management command, either.
> --
>     Do you have a source for this -- haven't heard of such a conflict -- 

There were patent questions around AAM. There are some discussions on the
t13 archive then it goes silent and nothing is ever said again, which I
imagine is when it got lawyered.

> besides, doesn't
> ATA-7 require some of those functions? 

No.

Alan

Re: Believed resolved: SATA kern-buffRd read slow: based on promise driver bug

[Robert Hancock]

Linda Walsh wrote:
> Mikael Pettersson wrote:
>> Linda Walsh writes:
>>  > Mikael Pettersson wrote:
>>  > > Linda Walsh writes:
>>  > >  > > Linda Walsh wrote:
>>  > >  > >>>> read rate began falling; (.25 - .3);  > >  > more 
>> importantly; a chronic error message associated
>>  > >  > with drive may be causing some or all of the problem(s):
>>  > >  > ---
>>  > >  > ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x2
>>  > >  > ata1.00: port_status 0x20080000
>>  > >  > ata1.00: cmd c8/00:10:30:06:03/00:00:00:00:00/e0 tag 0 cdb 0x0 
>> data 8192 in
>>  > >  >          res 50/00:00:3f:06:03/00:00:00:00:00/e0 Emask 0x2 
>> (HSM violation)
>>  > >  > ata1: limiting SATA link speed to 1.5 Gbps
>>  > >
>>  > > Looks like the Promise ASIC SG bug. Apply
>>  > > 
>> <http://user.it.uu.se/~mikpe/linux/patches/sata_promise/patch-sata_promise-1-asic-sg-bug-fix-v3-2.6.23> 
>>
>>  > > and let us know if things improve.
>>  > > /Mikael
>>  > ---
>>  >     Yep!  Hope that's making it into a patch soon or, at least 2.6.24.
>>  >     Kernel buffered
>> Good to hear that it solved this problem.
>> The patch is in 2.6.24-rc2 and newer kernels, and will be sent
>> to -stable for the 2.6.23 and 2.6.22 series.
>>   
> ---
>    Will 'likely' wait till -stable since I use the machine as a 'server'
> for just about any/everything that needs "serving" or "proxy" services.
>>  >  That and I'd like to find out why TCQ/NCQ doesn't work with the 
>> Seagate drives --
>>
>> The driver doesn't yet support NCQ.
> ----
>    Is 'main' diff between NCQ/TCQ that TCQ can re-arrange 'write'
> priority under driver control, whereas NCQ is mostly a FIFO queue?

First off one has to distinguish between ATA TCQ and SCSI TCQ. ATA TCQ 
is essentially abandoned, very few drives and fewer still controllers 
and matching drivers ever supported it.

SCSI TCQ has "head of queue", "ordered" and "simple" queueing modes. ATA 
NCQ effectively only has "simple" where the drive always decides what 
order to service the requests in. There is a FUA mode, which tells the 
drive that the command (normally a write) has to access the physical 
media before reporting completion.

> 
>    On a Journal'ed file system, isn't "write-order" control required
> for integrity?  That would seem to imply TCQ could be used, but
> NCQ doesn't seem to offer much benefit, since the higher level
> kernel drivers usually have a "larger picture" of sectors that need
> to be written.  The only advantage I can see for NCQ drives might

There are cases where writes need to complete in a specific order. This 
can be done either by using FUA bits (though libata doesn't do this by 
default currently) or by issuing cache flushes before and after certain 
commands.

> be that the kernel may not know the drive's internal physical
> structure nor where the disk is in its current revolution.  That could
> allow drive write re-ordering where based on the exact-current state
> of the drive that the kernel might not have access to, but it seems
> this would be a minor benefit -- and, depending on firmware,
> possibly higher overhead in command processing?

That's a big part of it. The kernel doesn't necessarily know what 
sectors will be the fastest to access at any given time whereas the 
drive can.

Also, NCQ has some other improvements that are independent of actually 
queueing commands - for instance, because the drive controls the DMA 
data transfer, it can transfer the data for one request in an 
out-of-order fashion instead of having to transfer to the host strictly 
from beginning to end as in traditional ATA.

> 
> Am trying to differentiate NCQ/TCQ and SAS v. SCSI benefits.
> It seems both support (SAS & SATA) some type of port-multiplier/
> multiplexor/ option to allow more disks/port.
> 
> However, (please correct?) SATA uses a hub type architecture while
> SAS uses a switch architecture.  My experience with network hubs vs.
> switches is that network hubs can be much slower if there is
> communication contention.  Is the word 'hub' being used in the
> "shared-communication media sense", or is someone using the term
> 'hub' as a [sic] replacement for a 'switch'?

I believe that they're essentially the same in that regard, though 
someone can correct me if I'm wrong..

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/

Re: SATA kernel-buffered read VERY slow (not raid, Promise TX300 card); 2.6.23.1(vanilla)

[Linda Walsh]

Alan Cox wrote:
>> rate began falling; at 128k block-reads-at-a-time or larger, it drops below
>> 20MB/s (only on buffered SATA).
>
> Try disabling NCQ - see if you've got a drive with the 'NCQ = no
> readahead' flaw.
---
   I'm not aware, off hand, how to disable NCQ.  I haven't had any
NCQ- or SATA- capable disks before a few weeks ago.

>>     The only way I could tell before was using hdparm to read the 
>> parameters. Since that doesn't work, it's hard to tell if they
>> are set correctly...
>
> hdparm supports identify to read modes on drives with libata. The one
> thing you cannot do is force modes right now.
>
>>     More importantly, how does one set parameters for acoustic and power
>> saving parameters?  Some of my disks are used as 'backup' devices for my
>
> hdparm or blktool
----

  I have hdparm-v7.7. 
There are some areas where it shows information, but areas where it
does not work jump out and lead me to suspect whether or not areas
that don't give explicit "ERROR" messages are presenting valid info.

Problem areas (using hdparm, disk=Seagate Barracuda 16MB cache, model=
ST3750640AS):
1) The drives current 'multicount' setting isn't readable or settable.
param "-i" shows "?16?" (with question marks around 16) and "-I" simply
shows "?" for the current setting.  Attempting to <read|set> it:
 "HDIO_<GET|SET>_MULTCOUNT failed: Inappropriate ioctl for device"
2) Drive Advanced Power Management setting("-B") (write-only):
 "HDIO_DRIVE_CMD failed: Input/output error"
3) Drive Acoustic ("-M"), read = " acoustic      = not supported",
write = " HDIO_DRIVE_CMD:ACOUSTIC failed: Input/output error"
   Note: drive detailed info from "-I" says:
        "Recommended acoustic management value: 254, current value: 0"
   (i.e. - there seems to be no way to set recommended value)
4) 32-bit IO setting ("-c") (don't know if this important given the disk's
raw-read speed, it may be meaningless for SATA)
 "IO_support    =  0 (default 16-bit)"*
*
FWIW -- the spindown/standby timeout ("S") does seem to work.

>> other computers.  With the ATA disks, they were kept "spun down" when not
>> being used (only used, 'normally', in early AM hours).
>
> Well for backup devices you can use the fact SATA is hot/warm plug.
---
    I don't follow. It is an internal drive.  Are their software "logically
unplug" commands that automatically re-"plug-in" the drive on access
and spin it back up like the spindown/standby timeout does?  Or were
you referring to SATA's general hot/warm plug ability (if my hardware
setup, drive-slots, etc, permitted removability)?
>
>>     Another new "problem" (not as important) -- even though SATA disks are
>> called with "sdX", my ATA disks that *were* at hda-hdc are now at hde-hdg.
>
> NOTABUG - your BIOS has decided to move them from the legacy addresses so
> they move from hda-d to e-g.
Sorry for my unclear usage -- by "problem" I meant that it was(is) an 
"unexpected behavior".  I'm sure the kernel is following the BIOS's
directions, I'm just not sure why a (supposedly), SATA-only card would
cause my BIOS to reserve 4 "[P]ATA-drives" after installing the
card.  It may be symptomatic of some "cost-cutting" measure by the
card manufacurer.  I just don't know why it's happening right now.

*however* -- it is "annoying" -- if the kernel reserves hda-hdd at the
request of the BIOS, it _might_ be useful if "udev" also populated
/dev/ with devices for hda-hdd.  I.e. -- "something" on the linux-kernel
software-side of things knows that hda-hdd aren't really their as
the devices are not created in the udev-managed filesystem upon boot.

It may not be a kernel-bug insomuch as the kernel is intended to work,
but it doesn't seem that it is a "valuable feature".  My reasoning:
"Hd" drive letters are "unstable" because plugging/unplugging HD
controllers and/or drives can change the HD lettering.  Consequently,
it is considered "best practice" to mount disks by label instead of
by drive letter under linux.  If it is acknowledged that the drive
letters are not stable, then why not have udev assign "hd" letters
only to drives that 'exist'? 

Conversely, if udev had 'reserved' (created) hda-hdd devices because
the BIOS said they were 'reserved', then I can see it might have some
usefulness.  This may be a 'udev'-specific concern or configuration
issue as well.  I ran into it as I was going to try to use LILO's
"drive=" and "bios=" params to move the disks back to start with 'hda',
but lilo refused, saying 'hda' didn't exist (which it doesn't, as
indicated in the /dev-mounted udev 'filesystem').  It's not something
impossible to workaround or fix, just seemed odd to move the working
drives up to hde-g, when they could have been mapped to hda-c with
no apparent conflicts. 

I know, it's a subtlety, but one not inconsistent with (wincing at
the admission of even knowing this, let along the comparison) WinXP's
feature set.

  If a disk was mounted and associated with a specific letter, then
later another controller or disk is added that would cause 're-lettering'
under linux, it won't necessarily cause re-lettering under WinXP (as
it used to under Win98).  This 'threw me' the first time it happened,
as I expected Win to 're-letter' my drives and it didn't.  It seems
to associate drive-UUID's with the last letter they were mounted at
(or tries to, barring conflicts).

Re: SATA kernel-buffered read VERY slow (not raid, Promise TX300 card); 2.6.23.1(vanilla)

[Robert Hancock]

Linda Walsh wrote:
> Alan Cox wrote:
>>> rate began falling; at 128k block-reads-at-a-time or larger, it drops 
>>> below
>>> 20MB/s (only on buffered SATA).
>>
>> Try disabling NCQ - see if you've got a drive with the 'NCQ = no
>> readahead' flaw.
> ---
>   I'm not aware, off hand, how to disable NCQ.  I haven't had any
> NCQ- or SATA- capable disks before a few weeks ago.

See here:

http://linux-ata.org/faq.html#ncq

> 
>>>     The only way I could tell before was using hdparm to read the 
>>> parameters. Since that doesn't work, it's hard to tell if they
>>> are set correctly...
>>
>> hdparm supports identify to read modes on drives with libata. The one
>> thing you cannot do is force modes right now.
>>
>>>     More importantly, how does one set parameters for acoustic and power
>>> saving parameters?  Some of my disks are used as 'backup' devices for my
>>
>> hdparm or blktool
> ----
> 
>  I have hdparm-v7.7. There are some areas where it shows information, 
> but areas where it
> does not work jump out and lead me to suspect whether or not areas
> that don't give explicit "ERROR" messages are presenting valid info.
> 
> Problem areas (using hdparm, disk=Seagate Barracuda 16MB cache, model=
> ST3750640AS):
> 1) The drives current 'multicount' setting isn't readable or settable.
> param "-i" shows "?16?" (with question marks around 16) and "-I" simply
> shows "?" for the current setting.  Attempting to <read|set> it:
> "HDIO_<GET|SET>_MULTCOUNT failed: Inappropriate ioctl for device"

I don't think you can get or get the multi count currently, it just uses 
the best supported value.

> 2) Drive Advanced Power Management setting("-B") (write-only):
> "HDIO_DRIVE_CMD failed: Input/output error"
> 3) Drive Acoustic ("-M"), read = " acoustic      = not supported",
> write = " HDIO_DRIVE_CMD:ACOUSTIC failed: Input/output error"
>   Note: drive detailed info from "-I" says:
>        "Recommended acoustic management value: 254, current value: 0"
>   (i.e. - there seems to be no way to set recommended value)

Not sure about these ones.. Does anything show up in dmesg when you do this?

> 4) 32-bit IO setting ("-c") (don't know if this important given the disk's
> raw-read speed, it may be meaningless for SATA)
> "IO_support    =  0 (default 16-bit)"*
> *

This setting is not meaningful for anything using DMA.

> FWIW -- the spindown/standby timeout ("S") does seem to work.
> 
>>> other computers.  With the ATA disks, they were kept "spun down" when 
>>> not
>>> being used (only used, 'normally', in early AM hours).
>>
>> Well for backup devices you can use the fact SATA is hot/warm plug.
> ---
>    I don't follow. It is an internal drive.  Are their software "logically
> unplug" commands that automatically re-"plug-in" the drive on access
> and spin it back up like the spindown/standby timeout does?  Or were
> you referring to SATA's general hot/warm plug ability (if my hardware
> setup, drive-slots, etc, permitted removability)?

I think they were referring to physically hotplugging the drive. This is 
more practical if you have a removable drive caddy, or if the drive is 
hooked up through eSATA.

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/

Re: SATA kernel-buffered read VERY slow (not raid, Promise TX300 card); 2.6.23.1(vanilla)

[Linda Walsh]

Robert Hancock wrote:
> Linda Walsh wrote:
>> Alan Cox wrote:
>>>> rate began falling; at 128k block-reads-at-a-time or larger, it 
>>>> drops below
>>>> 20MB/s (only on buffered SATA).
>>> Try disabling NCQ - see if you've got a drive with the 'NCQ = no
>>> readahead' flaw.
> http://linux-ata.org/faq.html#ncq
---
    When drive initializes, dmesg says it has NCQ (depth 0/32)
    Reading the queue_depth under /sys, shows a queuedepth of "1".

But more importantly -- I notice a chronic error message associate
with this drive that may be causing some or all of the problem:
---
Jan  2 20:06:10 Ishtar kernel: ata1.00: exception Emask 0x0 SAct 0x0 
SErr 0x0 action 0x2
Jan  2 20:06:10 Ishtar kernel: ata1.00: port_status 0x20080000
Jan  2 20:06:10 Ishtar kernel: ata1.00: cmd 
c8/00:10:30:06:03/00:00:00:00:00/e0 tag 0 cdb 0x0 data 8192 in
Jan  2 20:06:10 Ishtar kernel:          res 
50/00:00:3f:06:03/00:00:00:00:00/e0 Emask 0x2 (HSM violation)
Jan  2 20:06:13 Ishtar kernel: ata1: limiting SATA link speed to 1.5 Gbps
Jan  2 20:06:13 Ishtar kernel: ata1.00: exception Emask 0x0 SAct 0x0 
SErr 0x0 action 0x6
Jan  2 20:06:13 Ishtar kernel: ata1.00: port_status 0x20080000
Jan  2 20:06:13 Ishtar kernel: ata1.00: cmd 
c8/00:10:00:8b:04/00:00:00:00:00/e0 tag 0 cdb 0x0 data 8192 in
Jan  2 20:06:13 Ishtar kernel:          res 
50/00:00:0f:8b:04/00:00:00:00:00/e0 Emask 0x2 (HSM violation)
Jan  2 20:06:14 Ishtar kernel: ata1: exception Emask 0x10 SAct 0x0 SErr 
0x0 action 0x3
Jan  2 20:06:14 Ishtar kernel: ata1: hotplug_status 0x80
Jan  2 20:06:15 Ishtar kernel: ata1: exception Emask 0x10 SAct 0x0 SErr 
0x0 action 0x3
Jan  2 20:06:15 Ishtar kernel: ata1: hotplug_status 0x80
---
What da heck?  Note, this is with NCQ-queuing set to "1".  Only 
reference I could find for this error referred to "older drives", but 
this is a
2007-model year drive with ATA-7 and udma-6.

> I don't think you can get or get the multi count currently, it just 
> uses the best supported value.
ok
>
>> 2) Drive Advanced Power Management setting("-B") (write-only):
>> "HDIO_DRIVE_CMD failed: Input/output error"
>> 3) Drive Acoustic ("-M"), read = " acoustic      = not supported",
>> write = " HDIO_DRIVE_CMD:ACOUSTIC failed: Input/output error"
>
> Not sure about these ones.. Does anything show up in dmesg when you do 
> this?
---
    Yes:
    (for "-B", power-management)
ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x0
ata1.00: port_status 0x20200000
ata1.00: cmd ef/05:fe:00:00:00/00:00:00:00:00/40 tag 0 cdb 0x0 data 0
         res 51/04:fe:00:00:00/00:00:00:00:00/40 Emask 0x1 (device error)
ata1.00: configured for UDMA/133
ata1: EH complete
sd 1:0:0:0: [sdb] 1465149168 512-byte hardware sectors (750156 MB)
sd 1:0:0:0: [sdb] Write Protect is off
sd 1:0:0:0: [sdb] Mode Sense: 00 3a 00 00
sd 1:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't 
support DPO or FUA
----
   (for "-M" acoustic management):
ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x0
ata1.00: port_status 0x20200000
ata1.00: cmd ef/42:fe:00:00:00/00:00:00:00:00/40 tag 0 cdb 0x0 data 0
         res 51/04:fe:00:00:00/00:00:00:00:00/40 Emask 0x1 (device error)
ata1.00: configured for UDMA/133
ata1: EH complete
sd 1:0:0:0: [sdb] 1465149168 512-byte hardware sectors (750156 MB)
sd 1:0:0:0: [sdb] Write Protect is off
sd 1:0:0:0: [sdb] Mode Sense: 00 3a 00 00
sd 1:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't 
support DPO or FUA

Re: SATA kernel-buffered read VERY slow (not raid, Promise TX300 card); 2.6.23.1(vanilla)

[Mikael Pettersson]

Linda Walsh writes:
 > Robert Hancock wrote:
 > > Linda Walsh wrote:
 > >> Alan Cox wrote:
 > >>>> rate began falling; at 128k block-reads-at-a-time or larger, it 
 > >>>> drops below
 > >>>> 20MB/s (only on buffered SATA).
 > >>> Try disabling NCQ - see if you've got a drive with the 'NCQ = no
 > >>> readahead' flaw.
 > > http://linux-ata.org/faq.html#ncq
 > ---
 >     When drive initializes, dmesg says it has NCQ (depth 0/32)
 >     Reading the queue_depth under /sys, shows a queuedepth of "1".
 > 
 > But more importantly -- I notice a chronic error message associate
 > with this drive that may be causing some or all of the problem:
 > ---
 > Jan  2 20:06:10 Ishtar kernel: ata1.00: exception Emask 0x0 SAct 0x0 
 > SErr 0x0 action 0x2
 > Jan  2 20:06:10 Ishtar kernel: ata1.00: port_status 0x20080000
 > Jan  2 20:06:10 Ishtar kernel: ata1.00: cmd 
 > c8/00:10:30:06:03/00:00:00:00:00/e0 tag 0 cdb 0x0 data 8192 in
 > Jan  2 20:06:10 Ishtar kernel:          res 
 > 50/00:00:3f:06:03/00:00:00:00:00/e0 Emask 0x2 (HSM violation)
 > Jan  2 20:06:13 Ishtar kernel: ata1: limiting SATA link speed to 1.5 Gbps
 > Jan  2 20:06:13 Ishtar kernel: ata1.00: exception Emask 0x0 SAct 0x0 
 > SErr 0x0 action 0x6
 > Jan  2 20:06:13 Ishtar kernel: ata1.00: port_status 0x20080000
 > Jan  2 20:06:13 Ishtar kernel: ata1.00: cmd 
 > c8/00:10:00:8b:04/00:00:00:00:00/e0 tag 0 cdb 0x0 data 8192 in
 > Jan  2 20:06:13 Ishtar kernel:          res 
 > 50/00:00:0f:8b:04/00:00:00:00:00/e0 Emask 0x2 (HSM violation)
 > Jan  2 20:06:14 Ishtar kernel: ata1: exception Emask 0x10 SAct 0x0 SErr 
 > 0x0 action 0x3
 > Jan  2 20:06:14 Ishtar kernel: ata1: hotplug_status 0x80
 > Jan  2 20:06:15 Ishtar kernel: ata1: exception Emask 0x10 SAct 0x0 SErr 
 > 0x0 action 0x3
 > Jan  2 20:06:15 Ishtar kernel: ata1: hotplug_status 0x80
 > ---
 > What da heck?

Looks like the Promise ASIC SG bug. Apply
<http://user.it.uu.se/~mikpe/linux/patches/sata_promise/patch-sata_promise-1-asic-sg-bug-fix-v3-2.6.23>
and let us know if things improve.

/Mikael

Re:Believed resolved: SATA kern-buffRd read slow: based on promise driver bug

[Linda Walsh]

Mikael Pettersson wrote:
> Linda Walsh writes:
>  > Robert Hancock wrote:
>  > > Linda Walsh wrote:
>  > >>>> read rate began falling; at 128k block-reads-at-a-time or larger, it 
>  > >>>> drops below 20MB/s (only on buffered SATA).
>  > 
>  > But more importantly -- I notice a chronic error message associate
>  > with this drive that may be causing some or all of the problem:
>  > ---
>  > ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x2
>  > ata1.00: port_status 0x20080000
>  > ata1.00: cmd c8/00:10:30:06:03/00:00:00:00:00/e0 tag 0 cdb 0x0 data 8192 in
>  >          res 50/00:00:3f:06:03/00:00:00:00:00/e0 Emask 0x2 (HSM violation)
>  > ata1: limiting SATA link speed to 1.5 Gbps
>
>
> Looks like the Promise ASIC SG bug. Apply
> <http://user.it.uu.se/~mikpe/linux/patches/sata_promise/patch-sata_promise-1-asic-sg-bug-fix-v3-2.6.23>
> and let us know if things improve.
>
> /Mikael
>   
---
    Yep!  Hope that's making it into a patch soon or, at least 2.6.24.
    Kernel buffered

    I seem to remember reading about some problems with Promise SATA & ACPI.
Does this address that or is that a separate issue?  (Am using no-acpi for
now, but would like to try acpi again if it may be fixed (last time I tried
it with this card, "sdb" went "offline" (once it unmounted itself and
refused to be remounted (no error...just nothing), and another it stayed
mounted, but gave an I/O Error...so have been using no-acpi since).
An ACPI error in bootup said:
ACPI Exception (utmutex-0263): AE_BAD_PARAMETER, Thread EFFC2000 could 
not acquire Mutex [3] [20070126]

    Is the above bug mentioned/discussed in the linux-ide archives?  That
and I'd like to find out why TCQ/NCQ doesn't work with the Seagate drives --
my guess, since they say queuedepth of 0/32, is that they are blacklisted
as being drives that don't follow normal protocol or implement their
own proprietary extensions?  Sigh.  Really a lame move (if that's the case)
for Seagate, considering they usage they could likely get in server
configs.  Maybe they want to push their SCSI/SAS drives?

    BTW, can SATA have DPO or FUA or are those limited to SCSI?
Would it be a desirable future addition to remove the
"doesn't support DPO or FUA" error message" on SATA drives if they are
specific to SCSI?

Re: Believed resolved: SATA kern-buffRd read slow: based on promise driver bug

[Robert Hancock]

Linda Walsh wrote:
>    I seem to remember reading about some problems with Promise SATA & ACPI.
> Does this address that or is that a separate issue?  (Am using no-acpi for
> now, but would like to try acpi again if it may be fixed (last time I tried
> it with this card, "sdb" went "offline" (once it unmounted itself and
> refused to be remounted (no error...just nothing), and another it stayed
> mounted, but gave an I/O Error...so have been using no-acpi since).
> An ACPI error in bootup said:
> ACPI Exception (utmutex-0263): AE_BAD_PARAMETER, Thread EFFC2000 could 
> not acquire Mutex [3] [20070126]

Have you tried 2.6.24-rc6? If the problem still occurs there, you should 
post the full bootup log.

> 
>    Is the above bug mentioned/discussed in the linux-ide archives?  That
> and I'd like to find out why TCQ/NCQ doesn't work with the Seagate 
> drives --
> my guess, since they say queuedepth of 0/32, is that they are blacklisted
> as being drives that don't follow normal protocol or implement their
> own proprietary extensions?  Sigh.  Really a lame move (if that's the case)
> for Seagate, considering they usage they could likely get in server
> configs.  Maybe they want to push their SCSI/SAS drives?

Queue depth 0/32 means the drive supports a queue depth of 32 but the 
controller/driver don't support NCQ.

>    BTW, can SATA have DPO or FUA or are those limited to SCSI?
> Would it be a desirable future addition to remove the
> "doesn't support DPO or FUA" error message" on SATA drives if they are
> specific to SCSI?

ATA disks can have FUA support, but the support is disabled in libata by 
default. (There's a fua parameter on libata module to enable it I believe.)

Re: Re:Believed resolved: SATA kern-buffRd read slow: based on promise driver bug

[Mikael Pettersson]

Linda Walsh writes:
 > Mikael Pettersson wrote:
 > > Linda Walsh writes:
 > >  > Robert Hancock wrote:
 > >  > > Linda Walsh wrote:
 > >  > >>>> read rate began falling; at 128k block-reads-at-a-time or larger, it 
 > >  > >>>> drops below 20MB/s (only on buffered SATA).
 > >  > 
 > >  > But more importantly -- I notice a chronic error message associate
 > >  > with this drive that may be causing some or all of the problem:
 > >  > ---
 > >  > ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x2
 > >  > ata1.00: port_status 0x20080000
 > >  > ata1.00: cmd c8/00:10:30:06:03/00:00:00:00:00/e0 tag 0 cdb 0x0 data 8192 in
 > >  >          res 50/00:00:3f:06:03/00:00:00:00:00/e0 Emask 0x2 (HSM violation)
 > >  > ata1: limiting SATA link speed to 1.5 Gbps
 > >
 > >
 > > Looks like the Promise ASIC SG bug. Apply
 > > <http://user.it.uu.se/~mikpe/linux/patches/sata_promise/patch-sata_promise-1-asic-sg-bug-fix-v3-2.6.23>
 > > and let us know if things improve.
 > >
 > > /Mikael
 > >   
 > ---
 >     Yep!  Hope that's making it into a patch soon or, at least 2.6.24.
 >     Kernel buffered

Good to hear that it solved this problem.
The patch is in 2.6.24-rc2 and newer kernels, and will be sent
to -stable for the 2.6.23 and 2.6.22 series.

 >     I seem to remember reading about some problems with Promise SATA & ACPI.
 > Does this address that or is that a separate issue?  (Am using no-acpi for

sata_promise does nothing ACPI-related. It doesn't need to.
(Drives may be a different story.)

 >     Is the above bug mentioned/discussed in the linux-ide archives?

Yes.

 >  That
 > and I'd like to find out why TCQ/NCQ doesn't work with the Seagate drives --

The driver doesn't yet support NCQ.

Re: Believed resolved: SATA kern-buffRd read slow: based on promise driver bug

[Linda Walsh]

Mikael Pettersson wrote:
> Linda Walsh writes:
>  > Mikael Pettersson wrote:
>  > > Linda Walsh writes:
>  > >  > > Linda Walsh wrote:
>  > >  > >>>> read rate began falling; (.25 - .3); 
>  > >  > more importantly; a chronic error message associated
>  > >  > with drive may be causing some or all of the problem(s):
>  > >  > ---
>  > >  > ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x2
>  > >  > ata1.00: port_status 0x20080000
>  > >  > ata1.00: cmd c8/00:10:30:06:03/00:00:00:00:00/e0 tag 0 cdb 0x0 data 8192 in
>  > >  >          res 50/00:00:3f:06:03/00:00:00:00:00/e0 Emask 0x2 (HSM violation)
>  > >  > ata1: limiting SATA link speed to 1.5 Gbps
>  > >
>  > > Looks like the Promise ASIC SG bug. Apply
>  > > <http://user.it.uu.se/~mikpe/linux/patches/sata_promise/patch-sata_promise-1-asic-sg-bug-fix-v3-2.6.23>
>  > > and let us know if things improve.
>  > > /Mikael
>  > ---
>  >     Yep!  Hope that's making it into a patch soon or, at least 2.6.24.
>  >     Kernel buffered
> Good to hear that it solved this problem.
> The patch is in 2.6.24-rc2 and newer kernels, and will be sent
> to -stable for the 2.6.23 and 2.6.22 series.
>   
---
    Will 'likely' wait till -stable since I use the machine as a 'server'
for just about any/everything that needs "serving" or "proxy" services.
>  >  That and I'd like to find out why TCQ/NCQ doesn't work with the Seagate drives --
>
> The driver doesn't yet support NCQ.
----
    Is 'main' diff between NCQ/TCQ that TCQ can re-arrange 'write'
priority under driver control, whereas NCQ is mostly a FIFO queue?

    On a Journal'ed file system, isn't "write-order" control required
for integrity?  That would seem to imply TCQ could be used, but
NCQ doesn't seem to offer much benefit, since the higher level
kernel drivers usually have a "larger picture" of sectors that need
to be written.  The only advantage I can see for NCQ drives might
be that the kernel may not know the drive's internal physical
structure nor where the disk is in its current revolution.  That could
allow drive write re-ordering where based on the exact-current state
of the drive that the kernel might not have access to, but it seems
this would be a minor benefit -- and, depending on firmware,
possibly higher overhead in command processing?

Am trying to differentiate NCQ/TCQ and SAS v. SCSI benefits.
It seems both support (SAS & SATA) some type of port-multiplier/
multiplexor/ option to allow more disks/port.

However, (please correct?) SATA uses a hub type architecture while
SAS uses a switch architecture.  My experience with network hubs vs.
switches is that network hubs can be much slower if there is
communication contention.  Is the word 'hub' being used in the
"shared-communication media sense", or is someone using the term
'hub' as a [sic] replacement for a 'switch'?

Re: Believed resolved: SATA kern-buffRd read slow: based on promise driver bug

[Tejun Heo]

Linda Walsh wrote:
>    Is 'main' diff between NCQ/TCQ that TCQ can re-arrange 'write'
> priority under driver control, whereas NCQ is mostly a FIFO queue?

No, NCQ can reorder although I recently heard that windows issues
overlapping NCQ commands and expects them to be processed in order (what
were they thinking?).

The biggest difference between TCQ and NCQ is that TCQ is for SCSI while
NCQ is for ATA.  Functional difference includes more number of available
tags and ordered tags for TCQ.  The former doesn't matter for single
disk.  The latter may make some difference but on single disk not by much.

> Am trying to differentiate NCQ/TCQ and SAS v. SCSI benefits.
> It seems both support (SAS & SATA) some type of port-multiplier/
> multiplexor/ option to allow more disks/port.
> 
> However, (please correct?) SATA uses a hub type architecture while
> SAS uses a switch architecture.  My experience with network hubs vs.
> switches is that network hubs can be much slower if there is
> communication contention.  Is the word 'hub' being used in the
> "shared-communication media sense", or is someone using the term
> 'hub' as a [sic] replacement for a 'switch'?

Port multiplier is a switch too.  It doesn't broadcast anything and
definitely has forwarding buffers inside.  An allegory which makes more
sense is expander to router and port multiplier to switch.  Unless you
wanna nest them, they aren't that different.

-- 
tejun