PowerEdge R410 PERC 6/i SSD Hard Disk Upgrade configuration question

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PowerEdge R410 PERC 6/i SSD Hard Disk Upgrade configuration question

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My R410 is a host to various virtual machines running in a Hyper-V environment in Windows Server 2008 R2.

The original specification has been upgraded since supply (Service tag <ADMIN NOTE:Service tag removed per privacy policy>) as is now as follows:
PERC 6/i
3x 1TB SAS Seagate Barracuda ES.2 ST31000640SS 7200rpm 16MB Cache

The hard disks are configured in RAID5 and are fitted to the chassis in Dell hotswap caddies. There is one vacant bay in the chassis.

The purpose of the upgrade is to make the webserver virtual machine run faster by mounting its Hyper-V VHD file on a disk volume constructed from SSD drives. The proposed upgrade is 2x 64GB SSD drives operating in RAID installed in a Chieftec double 2.5" CTM-1322S caddy, fitted into the spare 3.5" drive bay.

HOM p86 "CAUTION: Combining SATA and SAS hard drives in the same system configuration is not supported."??

I am seeking clarification on the following:

1. What is the best option for connecting the two new drives? Can they be cabled to the PERC6/i or can the backplane accommodate the 3x SAS drives in combination with the 2x caddied SATA SSD drives?

2. If the PERC6/i can't be used, can I cable the two SSDs straight to the motherboard SATA connectors and setup the RAID in Windows disk management?

3. Is there anything I've missed or should be aware of?

Verified Answer
  • Yes, if you connect a SATA drive to the same controller as the SAS drives it will lower the signaling voltage to match the SATA drive.  This could cause performance degradation across all drives.

    This is why you should use an interposer.  One of the functions of the interposer is to allow SATA drives to operate at a higher signaling voltage.  If you use an interposer with the SATA SSD then it will operate at SAS signaling voltages.

    Thanks

    Daniel Mysinger

    Download the Dell Quick Resource Locator app today to access PowerEdge support content on your mobile device! (iOS, Android, Windows)

All Replies
  • Hello Chris

    What you are attempting is not a supported configuration, so I am unable to tell you if it will work.  The server is designed for 4 hard drives maximum.  The configuration you are proposing is dependant upon 3rd party equipment that I am not sure will work.

    Chris Murray

    HOM p86 "CAUTION: Combining SATA and SAS hard drives in the same system configuration is not supported."??

    SAS and SATA cannot be mixed in the same array.  You can have both SAS and SATA drives in the server at the same time, but just not in the same RAID array.

    Chris Murray

    1. What is the best option for connecting the two new drives? Can they be cabled to the PERC6/i or can the backplane accommodate the 3x SAS drives in combination with the 2x caddied SATA SSD drives?

    2. If the PERC6/i can't be used, can I cable the two SSDs straight to the motherboard SATA connectors and setup the RAID in Windows disk management?

    The backplane has 4 connectors, so it cannot accomodate 5 HDD's. However, the backplane is just a connector to the PERC.  The PERC supports a lot more than 5 HDD's.  If the double caddy allows both drives to be seen correctly by the controller then it should work. 

    Connecting the drives directly to the SATA ports on the system board will work. The problem is finding some way to do this.  There is not a location to mount the HDD's inside the server to reach these connectors. There is also not a cable path to reach the drive bays. If you find some way of cabling the drives to the SATA ports on the system board then the method you described should work. I would not bother with creating a software RAID on the drives as the point of RAID is redundancy and software RAID does not really provide redundancy.  The disks are not fully mirrored in a software RAID and if there is OS corruption the array is not recoverable.

    I hope that answers some of your questions, thanks.

    Daniel Mysinger

    Download the Dell Quick Resource Locator app today to access PowerEdge support content on your mobile device! (iOS, Android, Windows)

  • Hi Daniel, thank you for the answer.

    Would these seem to be my options?

    1. Find a caddy that multiplexes the 2 drives out on one SATA connector to be connected to the R410's backplane system.

    2. Settle for a single SSD, connect this via the R410 backplane and set up as a single volume in PERC to then mount the webserver vhd, taking care to schedule vhd snapshots onto the main 3 disk RAID array for backup

    DELL-Daniel My
    The backplane has 4 connectors, so it cannot accomodate 5 HDD's. However, the backplane is just a connector to the PERC.  The PERC supports a lot more than 5 HDD's.  If the double caddy allows both drives to be seen correctly by the controller then it should work.

    So the purpose of the PERC handling more drives than the R410 chassis and backplane can handle is because it's also used on larger systems whose backplanes have more bays? I'm assuming that the PERC has just the input from the chassis backplane, or does it also have SATA connectors for direct cable connection?

    DELL-Daniel My
    Connecting the drives directly to the SATA ports on the system board will work. The problem is finding some way to do this.  There is not a location to mount the HDD's inside the server to reach these connectors. There is also not a cable path to reach the drive bays. If you find some way of cabling the drives to the SATA ports on the system board then the method you described should work. I would not bother with creating a software RAID on the drives as the point of RAID is redundancy and software RAID does not really provide redundancy.  The disks are not fully mirrored in a software RAID and if there is OS corruption the array is not recoverable.

    My intention was to use RAID for the speed improvements rather than redundancy. I just wanted to fix and forget the hardware factor in the webserver performance optimisation.

  • I haven't seen a drive caddy that multiplexes 2x ssd's. Going for a single ssd is the next best option. This one 120GB SSD Corsair Force Series 3 Series SATA III is at a really good price point and is fast on a sata III interface so should perform well on a sata II port.

  • Yes, the PERC 6 is used throughout several of our servers.  The only reason you are limited to 4 HDD's on this server is becaue of the number of available connectors on the backplane.  The backplane is just a connector.  If that two drive caddy works properly then it should allow you to use both of the drives. The PERC 6 has two cable connections on it that connect to the backplane.  If you were to disconnect one of those cables then two slots on the backplane would not function.  The PERC is used across various platforms, so you can use normal cables from it as well.

    The single SSD is probably the best way to go.  If running two SSD's was primarily for performance gains then I would just go with one SSD.  Running two SSD's off of the PERC may increase performance a little, but running software RAID might actually slow down performance.  The calculations for software RAID all go through the CPU and memory on the system, so it will use more of those resources and could slow down during peak use times that tax those resources.

    Thanks

    Daniel Mysinger

    Download the Dell Quick Resource Locator app today to access PowerEdge support content on your mobile device! (iOS, Android, Windows)

  • If you run two SSD's generally you would mirror them no?    Or that is how many do it anyways.

  • As long as there are backups, then raid 0 or simple stripe would get the best from SSD's. If you follow the general guide lines for ssd then the mean time before failure can be 3 to 5 years. The 2 main ones are, don't defrag and don't index. These can shorten ssd life. Obviously in raid there's no trim support but the controller garbage collection should be enough.

  • I've been alerted to the possibility that the HOM may warn of mixing SATA/SAS on the same backplane because of the differing singalling voltages of the two technologies:

    "SAS uses higher signaling voltages (800-1600 mV TX, 275-1600 mV RX) than SATA (400-600 mV TX, 325-600 mV RX). When SAS is mixed with SATA, the
    SAS drives run at SATA-voltages."

    Daniel, would you please confirm if this is the case? If it is, perhaps I should opt for a a single 3.5" SAS SSD - They're more expensive than SATA SSD but seem to be higher performing units.

  • Yes, if you connect a SATA drive to the same controller as the SAS drives it will lower the signaling voltage to match the SATA drive.  This could cause performance degradation across all drives.

    This is why you should use an interposer.  One of the functions of the interposer is to allow SATA drives to operate at a higher signaling voltage.  If you use an interposer with the SATA SSD then it will operate at SAS signaling voltages.

    Thanks

    Daniel Mysinger

    Download the Dell Quick Resource Locator app today to access PowerEdge support content on your mobile device! (iOS, Android, Windows)

  • No 11G server that I know of enables the motherboard sata ports to run AHCI except the R210.  If AHCI is available on higher models (I know it isn't on the T710) please let me know!