Raid 0, 1, 3, 5 Asus A8N SLI hard raid 5

So I read the article on software raid 5. Tried it. :-(
Test info. 4 new 300G sata 7200 seagates. MB Asus A8N SLI Premium with AMD Dual 4400+ 2G DDR. Win XP SP2 x32 & x64 dual boot. Hacked XP Raid support.

History.
I have had 7 drives fail in the last 2 years.
2 siezed the bearings, 1 failed the controller but I swapped cards and recovered the data, 1 lost clusters - most data was recovered, 3 fused the motor drive chips when i connected them (AT133) onto an ATA 100 port or on a cable with seagate drives.

Anyway I felt that raid 5 would give me best of all worlds - speed plus redundancy - WRONG.

Details of tests.

1 drive with HD Tach 3.01. 65MB/s to 45MB/s (across the drive) & with a 2GB video file, copy in 35seconds = 58MB/s.

2 drive raid 0
SIL3112 hardware raid - 95MB/s - 95MB/s
NV Hardware Raid 105-120-110MB/s
3 drive raid 0
SIL3112 hardware raid 125MB/s - 125MB/s = PCI Bus limit
NV Hardware Raid 145-160-140MB/s
4 drive raid 0
SIL3112 125MB/s - 125MB/s = PCI Bus limit
NV Hardware Raid 190-210-180MB/s - whhoooo.

4 drive Raid 5 - block copy 2GB file from non raid 300G.
SIL3112 (You can do raid 5 in bios and can set it to boot) - 22MB/s (yes 200seconds for 2G)
NV - using hacked XP & dynamic disks - 6MB/s - oooooo!.
(248 seconds for 2GB file copy)

So I went looking for the reasons and found it here http://www.miracleas.com/BAARF/RAID5_versus_RAID10.txt
Please read it, then scrap those plans for raid 5.

I am now going to run sets of 2-drive-raid-0

Boot 2x 200G pata
5 partitions - Dual boot + Program files + MP3 + User files.
Backup Images 2x 200G sata
Video Data 2x 300G
Backup Video 2x 300G

Roms 120G

External 300G firewire.

Sigh!!!

RayM
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  1. Wusy.
    I have read your other posts.
    Don't be so...... It shows your .......

    FYI.
    I do know what I'm talking about. I have been studying raid issues for years on & off and the last 2 months intensivly.
    I have been in IT for .... well, since mainframes had toroid memory.. 1968?
    I built my first "pc" in 1979 in wire-wrap... Before the TRS80. Probably before your parents made a small mistake.

    Specifically.
    1. The drives I have are new seagate 7200 sata NCQ 8M cache.
    I only did write tests. Read tests were better than write but still less than 60MB/s. Remember that my MB has only a 3112? raid chip with a software raid 5 implementation, not an intel chip running at 500MHz.
    This is consumer stuff. Not $$$ enterprise.
    Spending $1000 on disks is bad enough without blowing another $1000 on a good raid card and a few $,000 more on a server board wih 64bit PCI slots.

    2. Servers use raid 5. I know that and if you had read that link you would understand that raid 5 is not recommended for hard disks with cache enabled and certainly not with Native Command Queuing. Both of which can readily lead to "dirty data" and a requirement to re-initilise the array after every start.
    3. Raid 5 is for large quantity/small file size servers. It is not for video streaming in the home. Raid 3 is much better for that. Go and look that up.

    4. I shut my pc off correctly at work tonight. Bought it home and when started up, the 2 dynamic-disk raid arrays were offline again. I had to reinitilise them.
    I had hoped that dynamic disk arrays may have been more robust than hardware raid, but maybe not.

    To summerise.
    Dont use raid 5 with modern, large disks for large files if you want performance.
    Use Raid 5 with 15KRPM scsi drives with small/no cache.
    Use expensive dedicated cards with it's own cache.


    RayM
  2. Software RAID is usually a bad idea anyway, but RAID 1 is easy on the CPU, and level 0 isn't too hard on the CPU either. RAID 0+1 gives you both, so I assume you're making your two level 0 arrays redundant?

    <font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
    <font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>
  3. Revise the chipset. I found the handbook. Its SIL 3114R not 3112.
    I also checked the notes I made. Read speed on the 4x300G raid 5 was 55MB/s on the 2G file copy.
    It's just the verification overhead on writing that's the bug.
    How does raid5 write work.... ?
    Read byte 1, read byte 2, read parity, check media is ok.
    Write byte 1, write byte 2, write parity.
    Verify byte 1, verify byte 2 verify parity. Ok, Next pair.

    For home media servers a better way would be:
    Write 4K block, write 4k block, write 4K parity block(like winpar).

    Read 4K block, read 4k block, read parity, verify.

    My winpar2 typically claims 400+MB/s verifying rar files...

    Do you know how to implement raid 3?
    Ray


    RayM
  4. Wow, RAID 3! I don't know how to set up Windows RAID, I've read the stuff and forgot it. Why? I'll never use it, I look at other people's results, mostly CPU overhead, and decide it's not for me!

    Having a dedicated parity drive should reduce the CPU overhead slightly, but I've always looked at hardware RAID where that doesn't much matter.

    <font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
    <font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>
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