RAID On versus AHCI

Good day,

I accidentally found Techquikie video by Sebastian Linus titled 'What is AHCI?', which is available in the following link:


After watching the video, I decided to check if any of my PCs is accidentally set to IDE all this time, and then change it to AHCI.

However, one of my workstation, a DELL Precision Tower 5810 has 1 more additional setting (beside IDE and AHCI), which is RAID on. All this time the workstation is set to RAID On.

Is it ok if I change the setting to AHCI or just leave it as RAID On? The reason why I want to change to AHCI is to get a fast SSD performance.

Thank you and have a nice day.

 

Hello. That is a great question that people often ask. The solution in your case is simple. Just leave it on RAID. If you change it the PC from RAID to AHCI it probably won't boot the OS any more. Plus, with RAID enabled it includes AHCI mode. In other words, you will gain nothing by changing the boot mode to AHCI because RAID uses AHCI already. RAID just has a broader feature set than if you select AHCI. Straight AHCI mode does not support RAID.

 

Actually, I have the intention to reformat the workstation because it was infected with trojan recently. Therefore, I think it might still be able to boot the OS if i change from 'RAID On' to 'AHCI' before formatting.

However, I've decided to leave the setting as 'RAID On' since you explained that all the features available for AHCI is also available in RAID.

Thank you very much and have a nice day.

 

You're welcome, friend. And, yes... if you reinstalled the OS it would boot fine.

To change from RAID to AHCI, or vice versa, you have to tweak registry settings in W7 before making the change in the BIOS. If you do not you will get a BSOD with "Inaccessible Boot Device" error and you will have to change it back or reinstall W7 to stop the BSOD.

With W8.X and W10, after changing the boot mode in the BIOS you have to next boot into Safe Mode so Windows can automatically change it in the registry, then reboot into normal Windows mode. If you do not you will get a BSOD with "Inaccessible Boot Device" error.

 

I asked the same question at Linus Tech Tips forum. One of them told me to switch to AHCI if I don't use the RAID function. May I know what is your opinion about this?

 

I think you might reduce boot time by the couple of seconds that raid takes to initiate after POST and that's it. As brother Fox mentioned it's better to go with raid incase you want to use all the goodies at a later date.
A friend of mine recently asked me the same thing when he built his computer. Despite my advice he went with AHCI simply because RAID being a non default option intimidated him. 2 weeks later he asked me if it's possible to raid another 1tb SSD with his original one...
There's nothing to loose going to RAID.

 

I agree with Brother @TBoneSan on this. People that recommend switching to AHCI from RAID often lack understanding about the differences between them. It has been this way for years. AHCI is not a problem (unless you want to create a RAID membership) and neither is RAID setting. There is no benefit to switching the BIOS setting, but most do not understand this. Switching to AHCI limits your options later on. If your system does not have capacity for multiple matching drives for a RAID membership or you are certain you will not want to use it, you can switch to AHCI and it will cause no harm in terms of performance. You will not see an increase in drive performance like switching from IDE to AHCI mode. Feel free to experiment though. No harm in doing so. Just don't use IDE.

If you have it set to RAID you can use Intel Rapid Storage Technology to create a RAID0 membership in Windows without having to reformat and reinstall the OS. You can also restore a drive image from a RAID0 array to a single drive or RAID0 membership with the BIOS set to RAID (as long as the amount of data fits on the single drive).

 

All right, understood. I'll stick/use with RAID for all my PCs that has RAID setting, but use AHCI for all my PCs that only have AHCI and IDE setting.

Thank you very much for the explanation.

 

Unless your doing redundent backup RAID requires both drives to be of matching size and volumes. ACHI is choose for drives that can be used of different size in the same system and reduces boot times as this doesn't require RAID checks in boot process. ACHI is choose form RAID for boot time and not to use redundent backup drives. This talk of RAID vs ACHI has no comparison one is used to do redundent backup and checks while one is just so you can use drives of varying size. This is why ACHI is by default so unless your doing Server backups then RAID would be the functions otherwise ACHI is more suited for every purpose.

 

Unless you use RAID0, which is an excellent and zero cost way to create a larger volume from two matching mechanical drives that are too small by themselves and it runs much faster than a single mechanical drive. I think both are frquently overrated by their proponents. There are pro and cons to both, and often too much silly bias in both camps. For the average user the choice is irrelevant. It is only when you have a specific need or desire that one matters more than the other. RAID is still the default boot mode on some systems and there is nothing adverse about it.

Unless shaving 1.5 to 2.0 seconds off the time to complete POST is super important the boot time is irrelevant. Personally, I think the improved performance of already slow HDDs running in a RAID0 membership is a lot more useful. The large volume size is also nice. To those that are excited about booting a second or two faster from power on to desktop wallpaper, AHCI is definitely the way to go. It is only a matter of individual preference. We all agree that IDE mode is the wrong choice.

 

Good day everyone. I decided to try the AHCI myself. If I'm satisfied with AHCI, I will stay with it. Otherwise, I will return to RAID. So far, I notice that AHCI is slightly faster than RAID. Thank you very much for the information, knowledge, opinions, and feedback. Have a nice day