Do Dell Perc Cards Really Support RAID 10
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Topic: Do Dell Perc Cards Really Support RAID 10
Posted By: davidshq
Subject: Do Dell Perc Cards Really Support RAID 10
Date Posted: 02 September 2005 at 4:08pm
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/ProductDetail.aspx?TabPage=techspecs&sku=340-2549&sp agenum=&category_id=277&brandid=&k=&c=us&l=en&cs=555&mnf=&prst=& prEnd=&mnfsku=&orderby=&searchtype=&pageb4search=&page=productlisting.aspx&i nstock=&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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- http://www.davemackey.net/" rel="nofollow - Dave Mackey - Virtual Home.
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Replies:
Posted By: theSCIENTIST
Date Posted: 02 September 2005 at 6:16pm
Yes, I remember reading about it way back, and I went through all RAID levels supported by PERC controllers, and RAID 10 is fully supported on PERC 3 and 4 series.
I have a PERC 4/SC on my PowerEdge and it fully supports RAID 10, however I have it RAIDing 1, the discs are fast enough (SCSI U320 10K rpms) no need to RAID 10, access is really fast even thou information is mirrored.
But if you realy want to be sure, go to (http://forums.us.dell.com/supportforums/board?board.id=pes_hardrive) ohh, hold, you already asked there, yeah, some of those guys are realy experts on Dell hardware, and they will tell you for sure.
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:: http://www.mylittlehost.com/ - www.mylittlehost.com
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Posted By: davidshq
Date Posted: 08 September 2005 at 4:50pm
Thanks. The information on the boards there was really confused. But I
ended up doing some benchmarking myself on a RAID 1 and RAID 10 as well
as a local HD and was able to show that it appears to be true RAID 10,
contrary to Dell's documentation.
David.
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- http://www.davemackey.net/" rel="nofollow - Dave Mackey - Virtual Home.
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