LSI SAS 2108 MegaRAID Power Save for Active/ Configured Drives


Today we are going to look at the LSI SAS 2108 power save feature for Active and Configured drives. For those wondering, the LSI SAS 2108 is an 8 port SAS 6.0gbps controller that supports parity RAID functions such as RAID 5. SAS 2108 cards can be found inexpensively as the IBM ServeRAID M5014 deal shows us. As I’m slowly setting up my new Home Server build, I’m starting to think about the long term use of the server. Its going to be on 24/7. Since money is not growing on trees, I need to keep the power bill to a minimum. My system main storage will be: 6x 2TB Hitachi 7k2000 Hard Drives in RAID5 each using 7.6w at idle = 45.6w total, I may at some point get 2 more and go RAID6. The RAID controller will be an LSI SAS 2108 based card.

45.6w at idle may not seem like a big deal as they consume about the same as 2x energy efficient light bulbs. Over a year it ads up. Let’s say 20 hours of idle a day =  912whr per day * 365 = 332.88Kwhr per year. In NZ each kwhr = about $0.25. That equals about $83.22 per year, just to keep the hard drives idle. $83 I can spend on other things like one beer a month for a year. Hitachi 7k200 drives are known for good performance and reliability but also noise. The disk noise is not excessive but audible all the same. Once the drives go into power save mode, there is a definite quieting from the server.

The LSI SAS 2108 is capable of power save mode for non-active and hot spare drives. All LSI SAS 2108 fimrware versions have these 2 options for power save mode. Firmware version 12.12.0-0048 for Sun/ Oracle brings us the ability to power save active drives also. Active drives are the drives in use and shown to the OS in an array be it single drive RAID 0 or a multi-drive RAID array.

LSI SAS 2108 Power Save in Action
LSI SAS 2108 Power Save in Action

I know most OS’s can do all this, turn drives off with power settings adjustments etc. But this is done via the controller. If you were booted in DOS, the drives would still power down. The only drawback is that spindled drives do take a few seconds to wind back up, so don’t expect instant access to your data. This is not meant for disks being accesses heavily 24/7.

LSI SAS 2108 Power Save Menu
LSI SAS 2108 Power Save Menu

The Dimmer Switch power save mode that the LSI MegaRAID is capable of (but only with Firmware v12.12.0-0048 from Sun/Oracle) also has the ability to cache activity to the drives while in power save mode. If the data fits in the cache the drives will not be spun up. This could be risky when the power is cut to the system and the cache is lost. Unless you are lucky enough to have the Cache Vault version of the LSI SAS 2108, or on a UPS that can last the power cut leaving data in drive cache may mean data loss. This do not read/write if data is or fits in cache can be turned off and data will not be cached while in power save mode.

I’m pretty happy with how it works and will probably use this in the build. This won’t be to everyone’s liking but hopefully for those that are interested this shows how one can do it. Now if only there was a newer version firmware for all cards that had this ability to use power save for active drives. For those wondering how to flash a SAS 2108 card, check the guide to flash the IBM ServeRAID 5014.


  1. Quoting a member of WHT:

    “LSI 2308 is PCIe 3.0 based, and it’s perfect for those new E5-26xx processors which have on-die 40-lane PCIe 3.0 conroller. PCIe 3.0 runs at 8 GT/s (PCIe 2.0: 5 GT/s), but the encoding has less overhead. As a result, PCIe 3.0 can deliver up to 1 GB full duplex per second per lane, which is twice as much as PCIe 2.0. so, I will predict PCIe 3.0 RAID cards based on LSI 2308 can have quite a bit performance jump, especially for those pure SSD based arrays.”

  2. Yes PCIe 3.0 can about double the throughput.
    But the SAS2008 and LSI2308 in IR/IT mode cannot do Active drive spin down via Hardware.

    Also anyone wanting to use Active drive spin down and Cachecade pro v2.0 are also out of luck as the driver that allows Active spin down does not support CacheCade Pro v2.0.

  3. I think LSI messed up big time with their cards. When I upgraded firmware on my 9260-4i i was shocked to see that powersave was gone for active drives. It took me some time to find somewhere on LSI site that starting with firmware XXYYZZ they just disabled powersave for active drives. So I had to go back to 2 year old firmware. I think it’s just crazy that they basically removed that option without any workarounds. 9260, 9265, Intel RS2BL080/040 and so on. I think no other RAID manufacturer does that.
    Below their explanation:

    “DS1 and DS2 are okay to use. DS3 should not be used, and has been disabled on newer versions of LSI MegaRAID 9260/9280 RAID controllers.

    In some cases, when Dimmer Switch with DS3 spins down the volume, the volume cannot spin up in time when I/O access is requested by the operating system. This can cause the volume to go offline, requiring a reboot to access the volume again.”

    I think they are hiding some issue with controller which causes problems – that’s why it was disabled.

  4. I’m still working on re-enabling, if possible.
    I found it very useful, did take a few seconds to wind back up, but I could live it as could the OS.

    LSI give us the choice.

  5. Great article, many thanks for writing it up. Can you tell me where exactly I need to go to get the Sun/oracle firmware version you noted? (12.12.0-0048)

  6. rmd3003, can you share which version of firmware you had to go with on the 9260 card to get the active drive power down?

  7. It’s possible to spin down inactive drives even when LSI firmware does no longer support it.
    Using smartmontools you can set the SMART standby time seperately for each RAID drive.
    Here is an example using Linux. For Windows the commands might be different.

    command line:

    smartctl -s standby,120 -d sat+megaraid,0 /dev/sda
    smartctl -s standby,120 -d sat+megaraid,1 /dev/sda
    smartctl -s standby,120 -d sat+megaraid,2 /dev/sda
    smartctl -s standby,120 -d sat+megaraid,3 /dev/sda
    smartctl -s standby,120 -d sat+megaraid,4 /dev/sda
    smartctl -s standby,120 -d sat+megaraid,5 /dev/sda

    File smartd.conf when using as daemon:

    # set standby time to 10 minutes for all RAID drives
    DEFAULT -H -e standby,120 -d removable
    /dev/sda -d sat+megaraid,0
    /dev/sda -d sat+megaraid,1
    /dev/sda -d sat+megaraid,2
    /dev/sda -d sat+megaraid,3
    /dev/sda -d sat+megaraid,4
    /dev/sda -d sat+megaraid,5

    smartctl -s standby,now -d sat+megaraid,0 /dev/sda
    you can spin down drives immediately.


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