On Mon, Dec 10 2007, Tejun Heo wrote:
There's one thing we can do to improve the situation tho. Several
drives including raptors and 7200.11s suffer serious performance hit if
sequential transfer is performed by multiple NCQ commands. My 7200.11
can do 100MB/s if non-NCQ command is used or
On Mon, 2007-12-10 at 16:33 +0900, Tejun Heo wrote:
There's one thing we can do to improve the situation tho. Several
drives including raptors and 7200.11s suffer serious performance hit if
sequential transfer is performed by multiple NCQ commands. My 7200.11
can do 100MB/s if non-NCQ
Tejun Heo wrote:
..
Mark, how is marvell PMP support going?
..
It will be good once it happens -- the newer 6042/7042 chips support
full FIS-based switching, as well as command-based switching,
with large queues and all of the trimmings.
Currently stuck in legalese, though.
Cheers
-
To
Jens Axboe wrote:
On Mon, Dec 10 2007, Tejun Heo wrote:
There's one thing we can do to improve the situation tho. Several
drives including raptors and 7200.11s suffer serious performance hit if
sequential transfer is performed by multiple NCQ commands. My 7200.11
can do 100MB/s if non-NCQ
Tejun Heo wrote:
..
NCQ is not more advanced than SCSI TCQ. NCQ is native and advanced
compared to old IDE style bus-releasing queueing support which was one
ugly beast which no one really supported well. The only example I can
remember which actually worked was first gen raptors paired with
Mark Lord wrote:
Alan Cox wrote:
The comment I saw, which I'm trying to verify, mentioned the SATA
drives held the bus or similar longer than SAS ones.
SATA normally uses one link per device so the device side isn't contended
unless you descend into the murky world of port multipliers.
..
(cc'ing Jens as it contains some discussion about IO scheduling)
Michael Tokarev wrote:
Richard Scobie wrote:
If one disregards the rotational speed and access time advantage that
SAS drives have over SATA, does the SAS interface offer any performance
advantage?
It's a very good question,
On Dec 1, 2007 2:43 AM, Richard Scobie [EMAIL PROTECTED] wrote:
Alan Cox wrote:
If you want really high performance use multiple drives, on multiple PCIE
controllers. Just make sure your backup planning of raid 1+0 setup is
done right as many drives means a lot more drive fails.
Thanks
Greg Freemyer wrote:
Also, if you have Port Multiplexers (PMPs) in use, that would be
interesting to know. I don't even know if PMPs are supported via SAS
controllers in 2.6.24 or not. ie. PMP support is new to 2.6.24 and
only a few Sata controllers will have PMP support in 2.6.24.
No,
Richard Scobie wrote:
Greg Freemyer wrote:
Also, if you have Port Multiplexers (PMPs) in use, that would be
interesting to know. I don't even know if PMPs are supported via SAS
controllers in 2.6.24 or not. ie. PMP support is new to 2.6.24 and
only a few Sata controllers will have PMP
Mark Lord wrote:
SATA port multipliers (think, hub) permit multiple drives
to be active simultaneously.
Quite true, although the host controller could artificially limit this,
giving the user a mistaken impression of their port multiplier being
limited to one-command-per-N-drives.
/nit
Jeff Garzik wrote:
Mark Lord wrote:
SATA port multipliers (think, hub) permit multiple drives
to be active simultaneously.
Quite true, although the host controller could artificially limit this,
giving the user a mistaken impression of their port multiplier being
limited to
Richard Scobie wrote:
Jeff Garzik wrote:
Mark Lord wrote:
SATA port multipliers (think, hub) permit multiple drives
to be active simultaneously.
Quite true, although the host controller could artificially limit
this, giving the user a mistaken impression of their port multiplier
being
Oh, more fiction:
Because SATA uses point-to-point connectivity, the scaling
available with SAS controllers is not possible with SATA
controllers. SATA drives must be connected on a one-to-one
basis with the SATA connectors on the controller – i.e, a fourport
SATA controller can connect up to
If one disregards the rotational speed and access time advantage that
SAS drives have over SATA, does the SAS interface offer any performance
advantage?
For example, assume a SAS drive and a SATA drive can both sustained
stream 70MB/s. A 16 drive JBOD SAS enclosure with internal SAS expander
First of all, I've yet to see a controller that is really able
to handle multiple requests in parallel. Usually, multiple
I/O threads gets exactly the same summary performance as a
single thread - UNLIKE of linux software raid which clearly
Thats usually true of hardware raid cards as they
Thanks for the comments.
It was really protocol/bus behaviour differences (if any), between SATA
drives in a SAS environment, vs SAS drives, that I am looking at.
I do know that SATA drives only support a subset of the SCSI commands
and wondered if the SAS drives were more clever in a multi
Alan Cox wrote:
The comment I saw, which I'm trying to verify, mentioned the SATA drives
held the bus or similar longer than SAS ones.
SATA normally uses one link per device so the device side isn't contended
unless you descend into the murky world of port multipliers.
..
And that's where
Richard Scobie wrote:
If one disregards the rotational speed and access time advantage that
SAS drives have over SATA, does the SAS interface offer any performance
advantage?
It's a very good question, to which I wish I have an answer myself ;)
Since I never tried actual SAS controllers with
The comment I saw, which I'm trying to verify, mentioned the SATA drives
held the bus or similar longer than SAS ones.
SATA normally uses one link per device so the device side isn't contended
unless you descend into the murky world of port multipliers.
On the host side an AHCI controller
Alan Cox wrote:
If you want really high performance use multiple drives, on multiple PCIE
controllers. Just make sure your backup planning of raid 1+0 setup is
done right as many drives means a lot more drive fails.
Thanks again. For what it's worth, I shall be attempting this with SATA
21 matches
Mail list logo
