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Community Member

UCS C210 M2 RAID Performance Issue

Hi all,

We have a C210 M2 Server with LSI 6G MegaRAID 9261-8i Card and factory shipped SAS Extender (up to 8 drives support).

We have 2 x 73Gb SAS 15K RPM Drives, and 5 x 600Gb SAS 10K RPM Drives.

We have setup a RAID 1 with the 73GB Drives and a RAID 5 with the 600GB drives managed by the MegaRAID card.

Whilst the configuration works, it is VERY slow. However, we have found that if we reduce the RAID 5 config from 5 to 4 drives the performance improves dramatically!

So my questions are;

1) I know there are two cables each attached to a bank of 4 drives but is this then a limitation to the number of drives you can have in a RAID 5 or can the the controller card SPAN the two banks of drives?

2) If the RAID can span over the 2 banks of drives what other configuration settings or tweaks do I need to do so we can get good performance from the deired configuration of RAID 1 + RAID 5?

Many thanks for your help.

Rod

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5 REPLIES
Cisco Employee

UCS C210 M2 RAID Performance Issue

Hello Rodney,

1) I know there are two cables each attached to a bank of 4 drives but is this then a limitation to the number of drives you can have in a RAID 5 or can the the controller card SPAN the two banks of drives?

LSI 9261-8i card can support 3 to 32 drives in RAID 5 configuration and can span across the backplane ports.

RAID 5 Overview, page 30

http://www.cisco.com/en/US/docs/unified_computing/ucs/3rd-party/lsi/mrsas/userguide/LSI_MR_SAS_SW_UG.pdf

http://www.cisco.com/en/US/products/ps10493/products_data_sheets_list.html

Can you please let us know how do you measure the RAID perrformance ?

Padma

Community Member

UCS C210 M2 RAID Performance Issue

Hi Padma,

I am measuring RAID performance using primarily CrystalDiskMark.  The main issue is with sequential write performance.  I've found that in a RAID 5 configuration with 5 drives the write performance is in the ballpark of 25-30MB/s.  When configuring the RAID 5 with only 4 drives, performance increases substantially to 380-400MB/s!

I am trying to determine if there are any other factors that could be causing this kind of performance degradation but I was hoping Cisco may know how to best configure a RAID 5 on this server.

Sincerely,

Chris Morgan

BASScom

Systems Engineer

Community Member

UCS C210 M2 RAID Performance Issue

I may have been premature in my assessment of the problem.

Now when using either 4 or 5 drives in RAID 5 I am consistently getting poor write performance.

Tested today using CrystalDiskMark and ATTO Disk Benchmark.

I have tried different combinations of drives, changed slots, changed different Virtual Disk properties but the problem remains.

At this point I am unsure what the cause is.

Chris

Cisco Employee

UCS C210 M2 RAID Performance Issue

Chris,

RAID performance depends upon number of factors.The following LSI doc could be used as reference sheet.

http://www.lsi.com/downloads/Public/Direct%20Assets/LSI/Benchmark_Tips_Jan_2010_v2_0.pdf

As per MegaRAID SAS User Guide , RAID 5 does not provide good write performance.

( Table 16: RAID Levels and Performance ,Page 38 )

Can you let us know the stipe size and write policies in your setup ?

Padma

Community Member

Re: UCS C210 M2 RAID Performance Issue

Disk array performs better with disk cache turn on. Make sure disk cache is on in your array config.

Sent from Cisco Technical Support iPad App

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