SB850 and RAID


I tried to find any info about peoples experience running raid 5 on AMD's SB850 Southbridge. But I was not able to find much online. So I would like to post my experiences...

I have a home server...
* AMD Phenom II 1055T
* Gigabyte GA-M880GA-UD3H
* 2*2 Gig + 2*4 gig Corsair "Value Select" RAM (12 GB Total)
* Running Windows 7 Ultimate (64 bit)

I have been playing with 4x 1.5TB Seagate 7200.11 Drives in RAID 5 (128kb stripe size - the controller only lets me chose between 64 and 128). The array is partitioned using GPT and formatted using NTFS.

Write speeds are between 30 and 60 MB/s averaging about 45 MB/s.
Read Speeds are between 180 and 250 MB/s averaging about 200 MB/s.
CPU usage seems to be minimal for this setup too.

So far I have been quite happy with the performance. I am quite new to running RAID arrays, but I think these numbers are quite good. I can copy across my gigabit network at 118MB/s!!!

I have a couple of questions...
1) Do I need to perform an initialization on a raid 5 array? Because the volume works without it...
2) Do I need to perform regular synchronizations?
3) Is it normal for synchronizations to take 20 to 30 hours for a 4.5TB array?

I am actually thinking of breaking the array and running 2 sets of RAID 0 arrays (3TB each) or a single raid 0 array, since 24/7 uptime isn't important to me, and I would get a nice performance increase, plus I have everything backed up elsewhere anyway...

Any other comments would be welcome....


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More about sb850 raid
  1. Just an update... I broke the raid 5 and tested out various raid 0 arrays...

    Using HDTune Pro I got read results of... (min / max / avg / Access time)..
    4 Drive RAID0 = 231 / 482 / 384 / 15.6
    3 Drive RAID0 = 176 / 375 / 295 / 15.8
    2 Drive RAID0 = 120 / 254 / 198 / 15.7
    Single Drive = 59 / 129 / 101 / 15.3

    Just in case someone else has been looking for info on the raid performance of AMD's SB850....

  2. Quick question about the SB850's raid abilities:

    1) can you make a 5 or 6 disk raid-5 array?

    2) can you expand a raid-5 array by adding a disk (like going from 3 - 4 disks, increasing
    the size but not deleting and re-creating the array)?

  3. "1) can you make a 5 or 6 disk raid-5 array?"

    I am not 100% sure, I only have 4 disks to play with, but I suspect that yes, you could. The only thing is that in the BIOS of the motherboard I have, the default setting left SATA3 ports 5 and 6 in IDE mode, so they could not be used in RAID mode... I changed this setting, but I don't have any more drives to play with on the controller.... Sorry!

    "2) can you expand a raid-5 array by adding a disk (like going from 3 - 4 disks, increasing the size but not deleting and re-creating the array)? "

    I don't think that is possible with any raid controller is it?

    Sorry, not really a big help!

  4. Thanks for the quick reply. So could you at least set all 6 drives into "raid" mode at the same
    time? I know you can't test it, but I at least wanted to know.

    I did some more research and there is conflicting information out there, but I am fairly sure
    I can build a 6-disk raid 5 array with the sb850.
    Also, it seems like the SB850 should be able to expand an array (like adding an additional
    disk to a raid-5, or raid-0 array without losing the data). But there seems to be some slightly
    tricky size limitations when expanding.

    On your questions about the raid-5 Arrays:

    You should probably perform an intialization of the raid array for a raid-5, as it will find
    if there are any problems anywhere.

    You do not need to perform regular synchronizations, but it is a little safer to do it once in a while
    or after there has been some kind of system issue.
    There is also something called a 'media check' that can be run regularly to make sure the media is
    continuing to hold the data correctly. That can be run weekly or monthly as well.
    It can take 20-30 hours to fully synchronize a 4.5TB array. The system likes to do it in sort of a
    "background" mode so it doesn't take too many system resources and allows you to keep working.

    Other thoughts:

    If you really can stand to lose all the data in a hard drive or system crash,
    then you can go with the raid 0 setups. But remember that you will lose everything
    since the last backup if it goes down. Also note that although rare, even power failures
    and system crashes can ruin a raid 0 volume, even if the disks are still fine. That makes
    losing all your data in a raid 0 more likely than if only a disk failure could cause a failure.
    If you don't overclock and have an uninteruptable power supply set to shut the machine
    down gracefully in the event of a longer power failure, you should be able to last a while
    with a raid 0 array.

    Personally, I use a raid 5 setup since write speed is not as important read speed to me
    and I don't want to have to backup that often or restore as it would take a LONG time.

    Remember also that you are limited to the speed of your network, so anything above the
    110MB / sec or so doesn't do you much good over the network.

    You also need to think a bit about how the drives are used. Are there many random I/O's
    going on or just large sequential reads and writes. Random favors raid 1 or raid 10 over
    raid 5 and 0 (0 can be the worst for many random reads).

    If speedy writes are critical, and you have some random reads, and you don't mind giving up
    half of your space for redundancy, then raid 10 is definitely the best. You didn't mention testing
    it before. It should give you almost 4-drive raid 0 read speeds and almost 2-drive raid 0 write speeds. You should check it out if it fits your needs.

    You could also do 2 raid 0's as you mentioned, it is another drive to manage, but you would
    only lose half your data if a drive failed.

    Good Luck, post back with any questions.
  5. "Thanks for the quick reply. So could you at least set all 6 drives into "raid" mode at the same time? I know you can't test it, but I at least wanted to know. "

    Yeah, that's right, I have all 6 ports set to "RAID" mode, and I can manage all 6 ports in "Raid Xpert"...

    Thank you very much for your info on raid arrays, especially the info on raid 5 syncs etc. I tried to find any kind of info about this, but there seems to be very little out there...

    My data consists of large files of which only 1 or 2 files are added every couple of days, so I don't have a problem running raid 0 and manually backing up else where....

    Anyway, thank you very much for your input!

  6. Just some additional information. I'm a fellow SB850 RAID5 user. Here's the hardware I'm using.

    Asus M4A88TD-V EVO/USB3
    AMD Phenom II X4 955
    Corsair Vengeance 2 x 4GB DDR3 @ 1600
    Corsair Professional 750AX
    BFG GeForce GTX 260 (free, was planning on using on board ATI 4250)
    5x 2TB Samsung Spinpoint F4 Sata II
    1TB Western Digital Caviar Black Sata II
    Fractal Design Define R3 Black (best case I've seen in my 20 years of building and servicing computers, only reason I list it... 9x HDD bays! SILENCE with 7 case fans, pretty loud GPU, and PSU/CPU fans at 50%)

    I've got the raid setup across both sets of SATA ports with no problems at all. Creating a 6 drive RAID seems to be entirely possible, though I don't have another 2TB drive that's not containing critical data, and I'm pretty well stuck on this being a Windows 7 box, which won't boot from USB (that I'm aware of).

    Settings are as follows GPT/NTFS/128kb stripe size (same as Dan's setup). My write speed is currently stuck around 30-33 MB/s over a gigabit link. Haven't benched read speed yet, though I'm sure it will more than saturate a gig link. When I get home, I'll be more than happy to bench both write and read, hopefully throw up a link to a graph too.

    Is it possible that the addition of drives increases the write penalty associated with parity? 33 MB/s is nice, but I've got 5.5TB to backup immediately with almost daily 40GB+ writes.

    Side note:
    A 7.3 TB drive is delicious, and does it play Crysis 2? [:tigsounds]
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