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Groups > comp.sys.ibm.pc.hardware.storage > #2264
| From | Arno <me@privacy.net> |
|---|---|
| Newsgroups | comp.sys.ibm.pc.hardware.storage |
| Subject | Re: IDE or AHCI ? |
| Date | 2012-01-04 19:19 +0000 |
| Message-ID | <9mjn1tFocqU3@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 <david@westcontrol.removethisbit.com> wrote: > On 04/01/2012 15:29, Yousuf Khan wrote: >> On 04/01/2012 2:53 AM, 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. >> >> 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. >> >> Yousuf Khan > NCQ can only really help if you have multiple outstanding transactions, > and the OS itself hasn't ordered them appropriately. Since the OS > (Windows or Linux) /does/ order transactions, NCQ will only help if the > OS is doing a bad 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), but on the other hand it knows nothing about which > processes are waiting for disk access, or the priorities of said > accesses, 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, and means that the OS's > IO subsystem must ensure the disk queue is completely empty before > sending the barrier write, and wait for it to finish completely before > sending anything else. If the disk handles transactions in the order > they are given, then such writes can be buffered better. Well, yes. Write-barriers are getting more and more important on Linux, with filesystems deferring more and using jourmalling more agressively. Looks like NCQ is basically obsolete. If I remember correctly, it is a thing that was brought on in SCSI disks a long time ago, when it still had merit. Not so anymore, just one more TLA that can be trhown at customers to make them think they are getting more for their money. Arno -- Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno@wagner.name GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F ---- Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans
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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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