Raid1 read performance (no benefit)

[DrParanoia]

Hi there!

 

I have an ASUS z170 DELUXE motherboard and today I decided to set up 2x3TB WD Blue HDDs in Raid1 mode for reliability (after my single 3TB started giving errors).

 

The thing is, when I setup them in Raid0 (in the BIOS), the read and write performance almost doubles, but in Raid1 mode there is no difference... Am I doing something wrong here?

 

Thanks in advance!

[mynameisjuan]

Raid one is just a redundancy. You will not see any benefit in speeds. Linus has some good videos on Raid if you are interested in using raid.

[bgibbz]

raid 0 = striping; data is split equally between two drives. Performance should essentially double.

 

Raid 1 = mirroring, data is simultaneously copied to two or more drives. There will be no performance benefit. 

[samcool55]

You are probably not aware of the differences between raid configs

Redundancy comes at a price

 

[Electronics Wizardy]

Don't use raid 1 here. use a backup. Raid 1 won't help you from a malware(like crypto locker) deleteing a file, corruption or many other problems

 

Also id stay far far away from motherboard raid and use storage spaces in windows indead.

[Megahurt]

Absolutely normal, RAID1 doesn't offer any performance boost, even in read only.

[DrParanoia]

Wow, that was fast! But i read that Raid1 should offer almost double the read performance since it is possible to read from 2 drives at a time. Or it's not the case?

[BrinkGG]

3 minutes ago, DrParanoia said:

Wow, that was fast! But i read that Raid1 should offer almost double the read performance since it is possible to read from 2 drives at a time. Or it's not the case?

Not true

Raid 1 just creates a copy of your data on a second disk. 

 

[mikat]

35 minutes ago, DrParanoia said:

Wow, that was fast! But i read that Raid1 should offer almost double the read performance since it is possible to read from 2 drives at a time. Or it's not the case?

No since it's reading the same data

[DrParanoia]

Just now, mikat said:

No since it's reading the same data

That's the point, if it's reading the same data, the read should be split between 2 disks  Is there a way to set it up like this? Maybe a software raid instead of hardware?

[mikat]

Just now, DrParanoia said:

That's the point, if it's reading the same data, the read should be split between 2 disks  Is there a way to set it up like this? Maybe a software raid instead of hardware?

how would you split the read data between 2 disks if the write data is the same??

and you can't do this, because of the way raid works, raid0 + backblaze would be a good option though

[DrParanoia]

2 hours ago, mikat said:

how would you split the read data between 2 disks if the write data is the same??

and you can't do this, because of the way raid works, raid0 + backblaze would be a good option though

You have the same data on 2 disks, that means you can read half of the data from each disk and combine it. How's this guy getting double the read performance?  https://foxdeploy.com/2015/10/30/windows-vs-intel-raid-performance-smackdown/

[mikat]

9 hours ago, DrParanoia said:

You have the same data on 2 disks, that means you can read half of the data from each disk and combine it. How's this guy getting double the read performance?  https://foxdeploy.com/2015/10/30/windows-vs-intel-raid-performance-smackdown/

I have no idea, but some digging around in Google suggests that it depends on the raid controller, many people get no read benefit and worse writes with raid 1 so you're not doing anything wrong.

[DrParanoia]

Okay, so I solved the issue (Though in a hacky way) and now I have roughly 240-250MB/s read from my Raid1 instead of usual 140MB/s!

 

So basically instead of using the motherboards drivers I went here https://downloadcenter.intel.com/download/25393/Intel-RSTe-AHCI-SCU-Software-RAID-driver-for-Windows- downloaded the archive and forced the installation of the Intel C600+/C220+ RAID Controller driver.

 

Guess it's a driver related issue, don't know why Intel still haven't fixed it...

[Trollend]

I can't believe the number of incorrect answers on this thread! I had to make an account just to reply to this post. Software engineer here. A properly implemented RAID 1 will absolutely double your read speeds! The OP is correct - because each piece of data exists in two different places at the same time, when loading a file, the computer is able to access half the requested data on one drive and half on the other drive. So your read speeds will double but your write speeds should be that of the slowest disk in your RAID, and not any worse.

 

Both SSDs and HDDs allocate data in sectors. Sectors are fixed size and represent the minimum storage unit of a drive. Typically, it's 512 bytes. So if you wanted to save a file that is 128 bytes, it would be stored in a sector of 512 bytes and the rest of the space in that sector would go unused. I tell you this because the only time you will not see double the read speeds is when the data you request is in a single sector, meaning the RAID controller cannot split the request between both drives. Practically speaking, this is a very rare situation and will never happen - and for a file so small the data access will be instantaneous anyways. Almost always, multiple sectors will be requested and the RAID controller can split up the sector requests between each drive - even if you're just accessing something as small as a single photo.

 

Your read speeds should double, and if you're not seeing this with whichever hardware/software RAID configuration you have setup, I would recommend you look into switching to a different RAID controller. For example, my old DDR3 Gigabyte motherboard (GA-EP45-UD3P) offered RAID 1 via the BIOS, but when I went through the configuration I did not see a boost to my read speeds. I decided to try Windows storage spaces out, which is a software RAID implementation, and then I did see double the read speeds on the created logical disk. So I can confirm that Windows storage spaces properly implements the performance RAID 1 should give.

 

That being said, I would not use Windows storage spaces for RAID. They have this ridiculous "resyncing" issue where if Windows crashes or shuts down abnormally (or you have Windows fast boot enabled, which it is by default), Windows will copy the entirety of one disk to the other to ensure they are synced up - even if the drives weren't in use when the computer crashed/was shut down. It doesn't matter if you barely have anything stored on your disk - if you have a 3 TB HDD, 3 TB of data will be copied from one disk to another to ensure a full sync. If you shut down your computer before the resyncing has finished, it has to start again from the beginning. So if you have a very large HDD, say 18 TB, you're looking at leaving your computer on for multiple days to ensure the resync finishes. It puts a ton of mileage on your drives for no reason, and a good RAID controller would not do this and would be smarter about knowing when data is possibly out of sync. If you want to know more, just Google "resyncing issue Windows storage spaces".

 

To summarize, there is a performance benefit - read speeds should double and write speeds should be that of the slowest drive.