# Do Dell Perc Cards Really Support RAID 10



## davidshq

I have a big question. I'm posting it at several reputable forums in hopes that someone out there knows an answer. I work for a company that uses a number of Dell Servers with PERC cards to handle our RAID configurations. Recently I was assigned the task of setting up RAID 10's utilizing the PERC 3/DC, which is the main controller we use. I happened to stumble across some documentation on the Dell website which states that "On the PERC 2/SC, 2/DC, 3/SC, 3/DCL, 3/DC, and 3/QC controllers, RAID-10 is implemented as RAID-1 Concatenated." According to Dell's definition of Concatenation earlier in this same article, "Data fills up the first disk before it is written to the second disk." In other words, in a true RAID 10 one gets redundancy because all data is mirrored on two hard drives but one also gets data access optimization because the data has been striped across all the mirrors. In RAID 1C (as I have dubbed it) you get redundancy because all data is mirrored but you lost the access optimization because the data is written to the first hard drive until it is finished, the it goes on to the second and so on. Not only is there a data bottleneck as data is written, but also when it is accessed because the data needed is not likely to be on multiple drives and thus all requests focus (generally) on only one drive, creating a bottleneck.
	We intended to upgrade to a 4/DC to overcome this problem, however I wanted to "triple check" that the 4/DC supported true RAID 10 and the 3/DC (etc.) did not. I called DELL and after spending over an hour on the phone with them was told that they were unsure whether either the 3 or 4 series of PERC cards supported true RAID 10.
	My question is, does anyone know? Does any PERC card support true RAID 10?
	Here is the Dell product page that states that the 3/DC supports RAID 10: http://accessories.us.dell.com/sna/...age=productlisting.aspx&instock=&refurbished=
	Here is the Dell Documentation page that states that 3/DC does not support true RAID 10: http://support.ap.dell.com/docs/SOFTWARE/smarrman/marb31/ch3_stor.htm
	Anyone who can clear up this question will be our hero.
David.


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## dfloyd

*Perc4/DC & Raid10*

We experienced a similiar dilemma.  

We setup a Raid 10 on a Perc4/DC card with 14 drives in the same raid.  When we read/write to the drive, only a couple of drives would light up.  This got us curious as to why all drives didn't light up with Raid10.  That is when we researched and found info about Dell not doing true Raid10.  

We also did some benchmark testing with different raid configurations on the 4DC and found that Raid0 with even 2 drives was faster than the Raid10 with 14 drives.  We expected the Raid10 with 14 drives to be as fast as Raid0 with 7 drives.  Not so with the 4DC card doing the concatenation.


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