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Groups > comp.sys.ibm.pc.hardware.storage > #2267
| From | "Rod Speed" <rod.speed.aaa@gmail.com> |
|---|---|
| Newsgroups | comp.sys.ibm.pc.hardware.storage |
| Subject | Re: IDE or AHCI ? |
| Date | 2012-01-05 07:51 +1100 |
| Message-ID | <9mjsfgFe7oU1@mid.individual.net> (permalink) |
| References | <jdvhfu$5o3$1@dont-email.me> <4f03de83$1@news.bnb-lp.com> <hPWdnT07Memqm5nSnZ2dnUVZ7oadnZ2d@lyse.net> <4f046249$1@news.bnb-lp.com> <4aGdnUAOPIbQ9pnSnZ2dnUVZ8tadnZ2d@lyse.net> |
David Brown wrote > Yousuf Khan wrote >> David Brown wrote >>> NCQ won't make a significant difference in Linux, since it has >>> always had good algorithms to order disk accesses to minimise head >>> movement. It will sometimes make things worse, such as when the OS >>> wants to enforce a particular order (for transactions to filesystem >>> journals, for example). And NCQ doesn't help windows much either - >>> after all, it only applies when you do more than one thing at a time. And any modern OS is doing that all the time. >> I find that it doesn't even help even when multitasking. I monitor >> the disk subsection of the Resource Monitor regularly, and very >> often when the disk is busy the Disk Queue Length is over 1.00 >> (meaning more than 1 process is actively waiting on the disk) and the Active Time is pegged near 100%. Nothing that >> can be done about it till SSD's are more affordable. > NCQ can only really help if you have multiple outstanding transactions, Yes. > and the OS itself hasn't ordered them appropriately. Yes. > Since the OS (Windows or Linux) /does/ order transactions, NCQ will only help if the OS is doing a bad job. It will also help when it can do a better job. > The disk knows a bit more than the OS regarding disk ordering (since it knows the full 3D geometry, rather than just a > linear LBA number), And so it can do a much better job when knowing that allows it to decide what ordering makes sense, something the OS can never do, most obviously with what is currently the biggest variable now, when something has just gone past the heads and you will need to wait an entire revolution before it shows up again. > but on the other hand it knows nothing about which processes are waiting for disk access, or the priorities of said > accesses, The OS doesnt necessarily know that either except with what it initiates itself. > and it knows nothing about barrier writes. I don't know how Windows handles write barriers, but on Linux they are > important to ensure the integrity of critical disk accesses such as journalling - they ensure that > everything that was supposed to be written earlier /has/ been written. NCQ totally screws this up, Not if the OS allows for it being there. > and means that the OS's IO subsystem must ensure the disk queue is completely empty before sending the barrier write, Wrong. > and wait for it to finish completely before sending anything else. Wrong. > If the disk handles transactions in the order they are given, then such writes can be buffered better. Wrong.
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IDE or AHCI ? Lynn McGuire <lmc@winsim.com> - 2012-01-03 12:30 -0600
Re: IDE or AHCI ? Arno <me@privacy.net> - 2012-01-03 21:05 +0000
Re: IDE or AHCI ? "arno fucker" <af@arnofucker.com> - 2012-01-04 12:41 +1100
Re: IDE or AHCI ? "Rod Speed" <rod.speed.aaa@gmail.com> - 2012-01-04 12:58 +1100
Re: IDE or AHCI ? Yousuf Khan <bbbl67@spammenot.yahoo.com> - 2012-01-04 00:07 -0500
Re: IDE or AHCI ? David Brown <david@westcontrol.removethisbit.com> - 2012-01-04 08:53 +0100
Re: IDE or AHCI ? "Rod Speed" <rod.speed.aaa@gmail.com> - 2012-01-04 20:32 +1100
Re: IDE or AHCI ? David Brown <david@westcontrol.removethisbit.com> - 2012-01-04 14:44 +0100
Re: IDE or AHCI ? "Rod Speed" <rod.speed.aaa@gmail.com> - 2012-01-05 07:37 +1100
Re: IDE or AHCI ? David Brown <david.brown@removethis.hesbynett.no> - 2012-01-04 22:56 +0100
Re: IDE or AHCI ? "Rod Speed" <rod.speed.aaa@gmail.com> - 2012-01-05 09:48 +1100
Re: IDE or AHCI ? Ed Light <nobody@nobody.there> - 2012-01-04 21:40 -0800
Re: IDE or AHCI ? Mike Tomlinson <mike@jasper.org.uk> - 2012-01-05 05:37 +0000
Re: IDE or AHCI ? "Rod Speed" <rod.speed.aaa@gmail.com> - 2012-01-05 17:37 +1100
Re: IDE or AHCI ? Yousuf Khan <bbbl67@spammenot.yahoo.com> - 2012-01-04 09:29 -0500
Re: IDE or AHCI ? David Brown <david@westcontrol.removethisbit.com> - 2012-01-04 16:04 +0100
Re: IDE or AHCI ? Arno <me@privacy.net> - 2012-01-04 19:19 +0000
Re: IDE or AHCI ? David Brown <david.brown@removethis.hesbynett.no> - 2012-01-04 23:14 +0100
Re: IDE or AHCI ? Arno <me@privacy.net> - 2012-01-05 08:47 +0000
Re: IDE or AHCI ? "Rod Speed" <rod.speed.aaa@gmail.com> - 2012-01-05 07:51 +1100
Re: IDE or AHCI ? Arno <me@privacy.net> - 2012-01-04 19:16 +0000
Re: IDE or AHCI ? "Rod Speed" <rod.speed.aaa@gmail.com> - 2012-01-05 07:41 +1100
Re: IDE or AHCI ? Yousuf Khan <bbbl67@spammenot.yahoo.com> - 2012-01-05 14:44 -0500
Re: IDE or AHCI ? "Rod Speed" <rod.speed.aaa@gmail.com> - 2012-01-06 17:35 +1100
Re: IDE or AHCI ? Krypsis <krypsis@optusnet.com.au> - 2012-01-07 00:05 +1100
Re: IDE or AHCI ? Arno <me@privacy.net> - 2012-01-06 20:04 +0000
Re: IDE or AHCI ? Mike Tomlinson <mike@jasper.org.uk> - 2012-01-06 21:13 +0000
Re: IDE or AHCI ? cjt <cheljuba@prodigy.net> - 2012-01-06 20:42 -0600
Re: IDE or AHCI ? David Brown <david.brown@removethis.hesbynett.no> - 2012-01-07 13:48 +0100
Re: IDE or AHCI ? Arno <me@privacy.net> - 2012-01-07 14:09 +0000
Re: IDE or AHCI ? Mike Tomlinson <mike@jasper.org.uk> - 2012-01-07 14:36 +0000
Re: IDE or AHCI ? Krypsis <krypsis@optusnet.com.au> - 2012-01-08 02:11 +1100
Re: IDE or AHCI ? Mike Tomlinson <mike@jasper.org.uk> - 2012-01-09 12:06 +0000
Re: IDE or AHCI ? Arno <me@privacy.net> - 2012-01-09 16:27 +0000
Re: IDE or AHCI ? Mike Tomlinson <mike@jasper.org.uk> - 2012-01-09 17:36 +0000
Re: IDE or AHCI ? Mike Tomlinson <mike@jasper.org.uk> - 2012-01-09 17:41 +0000
Re: IDE or AHCI ? Winniethepooh@100acrewoods.net (GMAN) - 2012-01-09 19:07 +0000
Re: IDE or AHCI ? David Brown <david.brown@removethis.hesbynett.no> - 2012-01-09 20:12 +0100
Re: IDE or AHCI ? Mike Tomlinson <mike@jasper.org.uk> - 2012-01-09 21:00 +0000
Re: IDE or AHCI ? Yousuf Khan <bbbl67@spammenot.yahoo.com> - 2012-01-09 11:31 -0500
Re: IDE or AHCI ? David Brown <david.brown@removethis.hesbynett.no> - 2012-01-07 17:10 +0100
Re: IDE or AHCI ? Mike Tomlinson <mike@jasper.org.uk> - 2012-01-10 14:18 +0000
Re: IDE or AHCI ? Yousuf Khan <bbbl67@spammenot.yahoo.com> - 2012-01-09 11:23 -0500
Re: IDE or AHCI ? Arno <me@privacy.net> - 2012-01-09 16:30 +0000
Re: IDE or AHCI ? David Brown <david.brown@removethis.hesbynett.no> - 2012-01-09 20:16 +0100
Re: IDE or AHCI ? cjt <cheljuba@prodigy.net> - 2012-01-09 17:13 -0600
Re: IDE or AHCI ? "Rod Speed" <rod.speed.aaa@gmail.com> - 2012-01-07 08:11 +1100
Re: IDE or AHCI ? Krypsis <krypsis@optusnet.com.au> - 2012-01-08 01:23 +1100
Re: IDE or AHCI ? "Rod Speed" <rod.speed.aaa@gmail.com> - 2012-01-08 06:43 +1100
Re: IDE or AHCI ? JW <none@dev.null> - 2012-01-09 05:23 -0500
Re: IDE or AHCI ? Yousuf Khan <bbbl67@spammenot.yahoo.com> - 2012-01-09 10:24 -0500
Re: IDE or AHCI ? "Rod Speed" <rod.speed.aaa@gmail.com> - 2012-01-10 09:34 +1100
Re: IDE or AHCI ? Yousuf Khan <bbbl67@spammenot.yahoo.com> - 2012-01-09 20:04 -0500
Re: IDE or AHCI ? "Rod Speed" <rod.speed.aaa@gmail.com> - 2012-01-10 15:33 +1100
Re: IDE or AHCI ? Arno <me@privacy.net> - 2012-01-06 09:48 +0000
Re: IDE or AHCI ? Yousuf Khan <bbbl67@spammenot.yahoo.com> - 2012-01-09 11:35 -0500
Re: IDE or AHCI ? David Brown <david.brown@removethis.hesbynett.no> - 2012-01-09 20:23 +0100
Re: IDE or AHCI ? Arno <me@privacy.net> - 2012-01-10 11:31 +0000
Re: IDE or AHCI ? Yousuf Khan <bbbl67@spammenot.yahoo.com> - 2012-01-20 06:54 -0500
Re: IDE or AHCI ? Arno <me@privacy.net> - 2012-01-04 19:14 +0000
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