While working with some new motherboards, I decided to do some testing. Since most motherboards ship with AHCI disabled and we needed hotplug for a new project, I wanted to do some testing to see if there was going to be a performance hit by using the AHCI drivers rather than the piix driver.<\/p>\n
To make sure we have a very stable benchmark, the same machine, without any changes other than switching AHCI on through the BIOS was tested twice. Granted, this is an older motherboard in a machine used for testing and development, the results on other motherboards should be similar.<\/p>\n
The difference in the input\/output and seeks are negligible. The sequential create and delete results generally show much improved results for create\/delete but the read results are virtually unchanged. This is probably a result of the Native Command Queuing (NCQ) enabled in AHCI that isn’t present in the piix driver. Since the firmware on the disk can reorder requests based on the rotational position of the data it needs to access, there are some benefits.<\/p>\n
Since it doesn’t appear to be detrimental to enable AHCI, and it does increase performance of two particular portions of the benchmark that may not really be exercised in a normal webserver environment, if you have the ability to run your hardware in AHCI mode rather than the native piix mode, I would suggest using AHCI.<\/p>\n
piix results:<\/h3>\n\r\nVersion 1.96 ------Sequential Output------ --Sequential Input- --Random-\r\nConcurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--\r\nMachine Size K\/sec %CP K\/sec %CP K\/sec %CP K\/sec %CP K\/sec %CP \/sec %CP\r\nkvm 4G 439 99 52686 15 27168 5 2039 99 62782 4 228.9 3\r\nLatency 48125us 1645ms 1545ms 16144us 137ms 863ms\r\nVersion 1.96 ------Sequential Create------ --------Random Create--------\r\nkvm -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--\r\n files \/sec %CP \/sec %CP \/sec %CP \/sec %CP \/sec %CP \/sec %CP\r\n 384 17299 43 379058 99 777 1 24781 49 522877 100 579 1\r\nLatency 1773ms 169us 18519ms 1403ms 14us 14935ms\r\n1.96,1.96,kvm,1,1252886317,4G,,439,99,52686,15,27168,5,2039,99,62782,4,228.9,3,384,,,,,17299,43,379058,99,777,1,24781,49,522877,100,579,1,48125us,1645ms,1545ms,16144us,137ms,863ms,1773ms,169us,18519ms,1403ms,14us,14935ms\r\n<\/pre>\nAHCI results:<\/h3>\n\r\nVersion 1.96 ------Sequential Output------ --Sequential Input- --Random-\r\nConcurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--\r\nMachine Size K\/sec %CP K\/sec %CP K\/sec %CP K\/sec %CP K\/sec %CP \/sec %CP\r\nkvm 4G 430 98 52639 14 27533 5 2066 99 62991 4 224.5 1\r\nLatency 50870us 1532ms 1655ms 10203us 21423us 953ms\r\nVersion 1.96 ------Sequential Create------ --------Random Create--------\r\nkvm -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--\r\n files \/sec %CP \/sec %CP \/sec %CP \/sec %CP \/sec %CP \/sec %CP\r\n 384 28173 56 373407 98 1645 2 31110 61 522376 99 1026 1\r\nLatency 1363ms 157us 12877ms 1216ms 61us 11397ms\r\n1.96,1.96,kvm,1,1252887577,4G,,430,98,52639,14,27533,5,2066,99,62991,4,224.5,1,384,,,,,28173,56,373407,98,1645,2,31110,61,522376,99,1026,1,50870us,1532ms,1655ms,10203us,21423us,953ms,1363ms,157us,12877ms,1216ms,61us,11397ms\r\n<\/pre>\nOutput from lspci -vvnn<\/strong> with the piix driver selected:<\/p>\n\r\n00:1f.2 IDE interface [0101]: Intel Corporation 82801H (ICH8 Family) 4 port SATA IDE Controller [8086:2820] (rev 02) (prog-if 8a [Master SecP PriP])\r\n\tSubsystem: Super Micro Computer Inc Device [15d9:8780]\r\n\tControl: I\/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-\r\n\tStatus: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- SERR- \nOutput from lspci -vvnn<\/strong> with the ahci driver selected:<\/p>\n\r\n00:1f.2 SATA controller [0106]: Intel Corporation 82801HB (ICH8) 4 port SATA AHCI Controller [8086:2824] (rev 02) (prog-if 01 [AHCI 1.0])\r\n\tSubsystem: Super Micro Computer Inc Device [15d9:8780]\r\n\tControl: I\/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+\r\n\tStatus: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- SERR- \r\n\tKernel driver in use: ahci\r\n<\/perr><\/tabort><\/pre>\nTechnical Specs:<\/h3>\n
Debian\/Squeeze\/Sid (Testing)
\nSupermicro P4SBE Motherboard
\nIntel(R) Core(TM)2 CPU 6300 @ 1.86GHz<\/perr><\/tabort><\/p>\n
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While working with some new motherboards, I decided to do some testing. Since most motherboards ship with AHCI disabled and we needed hotplug for a new project, I wanted to do some testing to see if there was going to be a performance hit by using the AHCI drivers rather than the piix driver. To […]<\/p>\n
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