Raid 5 Question

Discussion in 'Storage & Backup' started by AndyB, May 4, 2005.

  1. AndyB

    AndyB Member

    Joined:
    Apr 29, 2004
    Messages:
    32
    Howdy,

    Considering upgrading and If I did would buy another 3 200Gig Seagate SATA drives with a GA-K8NF-9 and run a 4 disk RAID 5 array (I currently have one of these drives in my PC now)

    My question is if I do this will I need to wipe (or backup) my current drive when creating the raid setup or can I merge the data into the raid array.

    Thanks
     
  2. aegan

    aegan Member

    Joined:
    Jun 21, 2002
    Messages:
    1,959
    Location:
    Under The Bridge
    you'll need to initialise the raid array.
    that would more than likely result in the loss of data.

    someone please correctc me if im wrong
     
  3. silver6

    silver6 Member

    Joined:
    Nov 1, 2002
    Messages:
    966
    Location:
    Sydney
    You will loose your data. You will need to do a backup and restore.

    Don't expect great performance from the onboard RAID controller.
     
  4. worlok

    worlok (Banned or Deleted)

    Joined:
    Dec 23, 2001
    Messages:
    316
    Location:
    syd.nsw.au:2121
    raid 5 goes with the bios hence the motherboard... so new mobo = new raid 5 thus backup

    correct me if i'm wrong :D
     
  5. bsbozzy

    bsbozzy Member

    Joined:
    Nov 11, 2003
    Messages:
    3,925
    Location:
    Sydney
    Yeah but if theres data already on the hdd, then he goes and shoves it into a raid 5 array, say buhbye
     
    Last edited: May 4, 2005
  6. stalin

    stalin (Taking a Break)

    Joined:
    Jun 26, 2001
    Messages:
    4,581
    Location:
    On the move
    backup your data
    create and initialise your array
    restore your data

    3 easy steps :)
     
  7. OP
    OP
    AndyB

    AndyB Member

    Joined:
    Apr 29, 2004
    Messages:
    32
    Thanks for all the replies.

    I thought as much, just a pain to backup 200G worth of data.

    Can I ask someone to confirm/deny this? Is there anything wrong with the Sil 3114 raid controller on these boards in a RAID 5 configuration?
     
  8. stalin

    stalin (Taking a Break)

    Joined:
    Jun 26, 2001
    Messages:
    4,581
    Location:
    On the move
    all non hardware based RAID cards have crappy performance with RAID 5. RAID 5 does XOR calculations to determine partity bits which is a pretty CPU intensive and particular task. 'proper' hardware RAID cards have a 'CPU' built into the card which does this processing for you. normal onboard RAID controllers require the host CPU to do this, slowing down performance, in particular write performance.

    You could go RAID10.. but you loose half you storage capacity, but it will be fast and have some redundancy.
     
  9. Gumby

    Gumby Member

    Joined:
    Jun 27, 2001
    Messages:
    1,743
    Location:
    Brisbane
    They use the CPU, they have minimal caching.

    As opposed to top quality raid cards that do all their processing with onboard IC's and have large caches.

    Pretty much follows the rules of get what you pay for. $200 mothboard with onboard raid 5 won't match a $300 dedicated raid controller.
     
  10. OP
    OP
    AndyB

    AndyB Member

    Joined:
    Apr 29, 2004
    Messages:
    32
    Ah thanks for clearing that up.

    I knew this was the case with hardware vs software raid but thought being on board the mobo put them in the 'hardware' category.

    I suppose this isn't a huge issue for me as performance is not critical, just want some redundancy for the drive(s) that will house divx's/mp3s etc etc. Windows/programs will be on another drive.

    Thanks for your replies
     
  11. OP
    OP
    AndyB

    AndyB Member

    Joined:
    Apr 29, 2004
    Messages:
    32
    On the realisation that the onboard Sil 3114 controller still relies on CPU heavily for RAID 5 arrays, would I not be better to simply use the Windows software raid method as described in this Tom's hardware guide?
    http://www.tomshardware.com/storage/20041119/index.html

    If both methods have comparable performance then I figure I would be better using the inbuilt software RAID with windows due to its portability to other machines (no drivers/reliance on specific raid controller).

    I've been re-considering the idea of RAID 5 since and thought I might go with a Raid 1 and Raid 0+1 setup instead. Buy another 200Gig to match my current for the 0+1 and 2x250gig for the Raid 1. Less space in the end but don't have the performance hit and have have the bonus of a Raid 0 section for windows/programs.

    Another quick question, with a Raid 0+1 are you forced to split the HDD 50/50? If I went with the above option I would prefer 50gig/150gig allocated to 0/1 respectively.

    Thanks
     
  12. wardenm

    wardenm Member

    Joined:
    Jul 11, 2002
    Messages:
    348
    Location:
    Brisbane
    I have a 6 disk windows based software RAID5 which works fairly well. Only get about 12-15MB/s on writes, but I don't write much to that volume anyway.

    RAID 0+1 is when you mirror a stripe, so you need at least 4 drives for it, what you said doesn't really make sense, but you can have some of a drive allocated to a mirror and another part to a stripe.

    Intel's ICH6R chipset will support split RAID levels. Windows will do it easily as well. If you have 2x200GB's You could have a ~100GB mirror, and a ~200GB stripe, or any other variation.
     
    Last edited: May 5, 2005
  13. Grubs

    Grubs Member

    Joined:
    May 7, 2005
    Messages:
    97
    Location:
    Melbourne (East)
    Remember that a modern CPU is an order of magnitude more powerful than most hardware RAID XOR processors. Many people find that soft-raid performance exceeds anything but the most modern of hardware controllers.

    The benefit of a true hardware raid controller is not so much RAID performance but rather the lack of impact on the main CPU. The other major benefit is OS independence. You can blow away your OS and reinstall a different version or even family of OS without risking data loss. (even a windows to linux migration!). This becomes critical when your big RAID5 is so big that you have no way to back it up in the event that you might want to reconfigure it.
     
  14. OP
    OP
    AndyB

    AndyB Member

    Joined:
    Apr 29, 2004
    Messages:
    32
    Thanks for those replies,

    I'm thinking RAID 5 is going to be the best option as impact on CPU shouldn't be an issue as windows/programs/games will be on another drive not in the array so when playing games etc it won't be reading/writing to the array (short of minimal things like playing MP3s). Also its not a server and does not require extremely fast performance - it will be very rare that I'll be needing to move large amounts of data quickly on/off the array.

    Got 2 IDE older 40 gig drives now, 1 for windows/programs/games, 1 for temp stuff (windows temp, bittorrent/emule download etc) so I don't fragment my main drives and put 4 200gigs in the RAID 5 for storage of mp3s/divxs and anything else that needs redundancy.

    Cheers
     
  15. wardenm

    wardenm Member

    Joined:
    Jul 11, 2002
    Messages:
    348
    Location:
    Brisbane
    I'm not sure i'm with you on that one. They are obviously more powerful for general tasks, but XOR is a very specific operation. I have a A64 3500+, and I can only get about 12-15MB/s out of 6 WD2000JB's. In RAID0 these drives get 100MB/s easily. The CPU only goes up by about 10-15% but I think it is doing XOR's as fast as it can. Quality hardware controllers can often manage 30, 40 or 50 MB/s.

    AndyB, You're exactly right, there won't be any effect unless your actually doing something fairly intensive on the array. Everything else will run just as fast as always.
     
  16. OP
    OP
    AndyB

    AndyB Member

    Joined:
    Apr 29, 2004
    Messages:
    32
    Thanks wardenm.

    It is interesting as that is a significant performance decrease @ 12-15 mb/s, but the more I think about there will be no need to ever have the array performing at high speeds. It's purpose is purely to add some cheap redundancy to all the stuff that I would hate to lose, as mirroring 600GB worth of data would start getting very pricey. The extra $150 for the parity drive and the loss in performance is well worth the benefits of size/redundancy for my purpose.

    Now I just have to deicde whether to use windows software raid or the Sil 3114 controller. Portability of OS vs portability of motherboard. I think I'm more likely to want to keep the array on a different motherboard rather than change it to linux so the windows software option sounds the go.

    Cheers
     
    Last edited: May 7, 2005
  17. W.G.A.F

    W.G.A.F (Taking a Break)

    Joined:
    Dec 23, 2001
    Messages:
    584
    I'm using Raid-5 via onboard Sil3114 controller on Epox 8RDA6+Pro using 4x Seagate (7200.8) ST3250823AS 250GB drives. Raid array is being managed via the SATARAID5 software and setup via bios, ie not WindowsXP.

    As you, I thought about doing full software implementation via XP but in my case I decided against it because I simply don't trust XP to maintain the array and not oneday go belly up and take all my array and files it contains with it.

    I'm not certain of this but when I was looking for other references to using the Sil3114 controller I kept finding mention of a Raid-5 patch for XP which to me sounds as if XP doesn't needs to be "patched" to create and run a Raid-5 array anyway? Doesn't sound to appealing.

    Not all of the Sil3114 onboard controllers allow the setting up of Raid-5. With my motherboard it required a Raid-5 enabled bios from Epox and to date there has only been one beta available, so future bios updates are probably not going to be made available. A normal bios file for my board would remove Raid-5 function.

    If I was to update the motherboard I would probably have to transfer the files off or seek out another board with Sil3114 onboard. No big deal to me as I don't update motherboards often but hard drives I do so files will eventually be transferred to larger drives which will necesitate setting up another array to transfer across anyway .

    Below is a Sandra benchmark screenie of the above mentioned array using 128/64 stripe/cluster. Note the very low write performance.


    [​IMG]
    Click to view full-sized image!
    Hosted by UGBox Image Store


    CPU usage isn't too bad when array is being written to and is a lot lower than I expected. After I setup the array via Sil3114 bios screen and then subsequently formatted in windows the management software kicked in to restore redundancy across the drives. This process took about 6 hours to complete and even though the drives were in heavy use the CPU usage calculating parity information was mostly below 20% and system was still very usable.

    I'm still currently transferring files across to array having only set it up recently. Transfers are dog slow but I should have sufficient performance for reads and streaming once the files are on there.

    Heres a pic of the Sil3144 Raid-5 main management screen. It's actually quite different to the management software that is generally supplied with motherboards running the Sil3114 that don't support Raid-5 natively or without some mod such as mine.

    [​IMG]
    Click to view full-sized image!
    Hosted by UGBox Image Store


    Just for kicks I decided to have a play with Raid-0 prior to flashing bios to enable Raid-5 use. Stripe/cluster size is again 128/64 which seems to be best performing combo and possibly best setup anyway for my intended use which is to store huge video files only.

    [​IMG]
    Click to view full-sized image!
    Hosted by UGBox Image Store


    The Raid-0 figures with 4 drives above only see about 1-2% improvement over scores with only 3 drives, so definately running into PCI bus bandwidth problems.

    Anyway, I hope the above might be of some interest to those curious about Raid-5 on onboard Sil3114.
     
  18. worlok

    worlok (Banned or Deleted)

    Joined:
    Dec 23, 2001
    Messages:
    316
    Location:
    syd.nsw.au:2121
    would the write speed be slower or up to par when runnning a single drive compared to raid 5 array
     
  19. wardenm

    wardenm Member

    Joined:
    Jul 11, 2002
    Messages:
    348
    Location:
    Brisbane
    In my experience, slower if using software RAID5 or cheap hardware without a proper XOR processor. Probably faster with a quality hardware solution.
     
  20. OP
    OP
    AndyB

    AndyB Member

    Joined:
    Apr 29, 2004
    Messages:
    32
    Okay I've weighed up my options I think I might go with a hardware Raid 5 solution.
    Redundancy/size are the important features so the best I could do with 4x200 drives is a raid 0+1 which would only offer 400G, which the added bonus of great data rates. However for the sake of an extra $150 I can get a hardware RAID 5 solution and enjoy a 600Gb array with good performance. Software Raid 5 just seems to sacrifice a little too much performance.

    Also this way I can set this array up now rather than wait to upgrade as I can buy the card/drives and set it up now in my current PC and just move it into my new one in the future.

    Card wise, something like this be ok? Anyone able to justify any different cards? notice there were a few brands... promise etc.
    http://www.i-tech.com.au/products/5593_HighPoint_Rocket_Raid_1640___4_channel.asp

    Thanks once again for all your help

    Cheers
    Andy
     

Share This Page

Advertisement: