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Z97Extrem6 Raid with 6 SSD's

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Category: OverClocking(OC) Zone
Forum Name: OC Technical Discussion
Forum Description: OC enthusiast's tech talk
URL: https://forum.asrock.com/forum_posts.asp?TID=1182
Printed Date: 20 May 2024 at 11:27am
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Topic: Z97Extrem6 Raid with 6 SSD's
Posted By: sparks79
Subject: Z97Extrem6 Raid with 6 SSD's
Date Posted: 07 Nov 2015 at 3:49am
My System--- Z97Extreme6 with Latest Bios Firmware, 32gb Ram, Six Revo SSD's 120gb.
Using On-board Raid Connected in Raid0 Stripe, Windows 7 Pro x64.
I have Measured the Speed with HdTunePro.
With Two Drives ( Revo840 ) I get 1042Mb/s.
With Four ( Revo850 )I get 1547Mb/s.
With Six ( Two 840's + four 850's ) I get 1554Mb/s.
I can't understand whats wrong here, I thought with Six Drives the Speed would be Much Faster.
I can understand that with Raid and using conventional Disks that they all have to be the of the same Model , Size and Series.
But with SSD's from my understanding that it does not matter that the Raid will set the speed to the speed of the slowest drive.
So I can only think of three possibilities here;--
1-- I have reached whats called ( The Point of Diminishing Returns ).
2--- The On-board Raid is not intelligent enough to configure itself any faster.
3--- The Mixture of the drives is the Bottleneck.
I'm not prepared to Splash out more Cash on Two more 850's, just find I have the same problem.
Can anyone confirm if a Six Port Raid Card would give Faster Speed than 1554/mb/s with these Six Drives.



Replies:
Posted By: parsec
Date Posted: 09 Nov 2015 at 3:31pm
You have reached the total bandwidth limit of the Z97 SATA chipset at ~1,500MB/s. That was first encountered when the Z87 chipset was released, which is the first Intel chipset to provide six SATA III ports. That is clearly demonstrated in the speed difference between four and six drives, virtually none.

The resources for the SATA interface in the Z97 and earlier Intel chipsets is based on PCIe 2.0, with likely no more than eight - ten PCIe 2.0 lanes allocated to the six SATA III ports. Very little was said about this by RAID 0 SSD users, they just accepted it.

Are you aware that the speed of 1,500MB/s+ read and write only applies to large, single files in the range of ~0.5MB and greater? All file reads and writes are not done at 1,500MB/s. Small 4KB files are usually read by SSDs at 30 - 40MB/s, and the more drives added to a RAID 0 array causes the 4K read speed to decrease along with it.

The slowest SSD in the RAID array will limit the ultimate speed that is possible with all the drives combined. But that is still at the mercy of the intrinsic bandwidth limits of the storage controller, the SATA portion of the Z97 chipset.

I personally cannot answer your last question.


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