Does A8N-SLI Deluxe have Raid 5 online expansion?

Discussion in 'Asus' started by idon.wong, Nov 22, 2005.

  1. idon.wong

    idon.wong Guest

    Hi all,
    I'm considering getting the A8N-SLI Deluxe mobo with a dual core Athlon
    64 X2. I've read some articles which indicate the onboard Raid 5
    performance is somewhat lacking, but i'd like to try it out anyways
    before investing in a dedicated Raid5 card.

    Anyways, my question is, does anyone know if the board supports online
    expansion? I mean, if i build a parity array with 3 drives, can i add
    additional capacity later by adding another drive and rebuilding the
    array, without losing the existing data? I've read that this is a
    feature most dedicated raid cards have.

    Thanks,
    iDon
     
    idon.wong, Nov 22, 2005
    #1
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  2. idon.wong

    Paul Guest

    A real RAID card would get you an XOR engine (the chip with the
    heatsink) and a cache DIMM. Real RAID cards support in-place
    migration, so you can grow an array. These are not features
    you would expect from some $5 chip slapped on a motherboard.

    If you want speed and reliability, do a RAID 0+1 with four
    disks. You buy four disks, and get two disks capacity wise,
    which is worse economics, but the speed of the striped pairs
    more than makes up for it. It basically consists of two
    striped pairs, mirrored against one another.

    If you plan on using a RAID, I would also recommend the purchase
    of a UPS, so that the computer can go through an orderly shutdown
    during a power failure. Some UPSes have an interface, to signal
    to the computer, and the UPS software installed on the computer,
    can then shut the computer down when you are not present. That
    will help keep the two mirrored arrays synchronized, in the case
    of a 0+1.

    Also, if you want to play with RAID5, there was a recipe on
    Tomshardware, that would allow you to use vanilla drive interfaces
    to build a RAID. The speed of the RAID5 built this way, will
    emulate the performance to be expected from the A8N-SLI, so
    you can test the concept now, if you have enough disks.

    http://www.tomshardware.com/storage/20041119/index.html

    Paul
     
    Paul, Nov 22, 2005
    #2
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  3. Hi,
    I'm actually using this 'hack' to run a 6x250 Raid 5 Configuration
    (1,13TB). I've not measured the speed, but it is used as a fileserver,
    and my 'feel' is, that it runs about 40% of the speed of a single SATA
    drive.

    However the way Toms describe the hack of the files DOES NOT WORK any
    more, if you have a fully updated Windows XP SP2, one of the files
    (can't remember which one) is no longe ASCII but Binary - so you can't
    find the string to change. However there are people out there who have
    hacked the binary file and changed the string - I use these files for
    my raid.

    Works without any problem

    Regards Leif.
     
    Leif Nordmand Andersen, Nov 22, 2005
    #3
  4. idon.wong

    idon.wong Guest

    Thanks guys.

    My plan is to build a new machine to act as my home office server which
    would operate 24/7. Since it is going to be on all the time anyways, i
    figured i might as well make it my network file server too, rather than
    buy a seperate NFS like Buffalo's solution. Since it'd mostly be
    hosting media content (like photos, movies, music), for read
    operations, i thought the Raid 5 CPU hit might be ok (plus i'd have a
    dual core CPU). I'd have another set of drives (possibly mirrored) for
    the other applications to run (and write) off of. That raises another
    question - am I able to enable both raid controllers at the same time?

    Anyways, here are the specs I've got planned. Any thoughts?

    AMD Athlon 64 X2 3800+
    Asus A8N-SLI Deluxe
    OCZ PC3200 DDR400 Premier Series 1 Gb Dual Channel
    Asus GeForce 6200 128MB PCI-E
    Antec SLK3800B Mid Tower w 400W PSU
    4x Western Digital SATA 320GB drives
    2x Seagate ATA 200Gb (I have kicking around)
    DVD+/-RW drive

    My original question was aimed at whether i can save a few bucks now,
    not buy 1/4 320 Gb drives now, and add it later. Does the XP hack
    support expansion?

    Thanks,
    iDon
     
    idon.wong, Nov 23, 2005
    #4
  5. idon.wong

    Paul Guest

    I don't do RAID myself, as I only have desktop configs for
    computers, but some questions I'll ask anyway...

    1) What is your backup strategy ? Any time you plan on buying
    a whack of disks, with a large total capacity, do you plan
    on using that capacity ? Can you predict how many years it
    will take to fill it ? Is there any point going with 320GB
    drives ?

    2) If you have a backup strategy capable of dealing with the
    sum total of storage capacity you plan on the new machine,
    then in-place migration becomes a non-issue. Simply backup
    and restore. Your backup solution should be capable of
    backing up the whole array, in an overnight time period
    (say 8 hours, so you are not bumping into the backup the
    next day). If the backup method was sector-by-sector,
    no compression, and a disk managed 50MB/sec transfer
    speed, then in 8 hours you can transfer 1.44 Terabytes.
    That implies the backup solution itself doesn't have to
    be striped to work. File by file backup wouldn't be
    practical if your large array was full, but makes sense
    if the array is mostly empty (seek time is a killer on
    backups, as is softwqre compression).

    This is one reason you won't find any big drives in my house,
    because it would cost too much to back them up. Each computer
    gets a tiny drive, with a tiny backup requirement. An 80 GB
    drive, with a second 80GB drive as a cold backup device, is
    enough for me.

    No matter how a RAID is constructed, the disks are all connected
    to the same power supply, and are sitting in the same ATX
    metal box. A catastrophy, like a lightning blast, or a PSU
    failure that overvolts all the drives, will negate whatever
    redundancy is in the RAID array. That means, even if you
    bought a $600 RAID card, added hot spares etc., your array
    could still be destroyed in a millisecond.

    Tape is too expensive to make a decent backup method. Using
    disks is an alternative, but a proper rotation strategy would
    require more disk drives than you would be happy with. DVDs
    would probably be too slow in backup or restore, to meet
    an eight hour objective.

    I think your first engineering task, is figuring out how
    backups will work. Constructing the RAID array will seem
    trivial after that.

    Yes, you can run more than one array at a time on your board.

    Maybe a smaller array, with more emphasis on off-line
    storage of stale content, would make more sense. You could
    probably afford to buy smaller disks, and make your RAID
    a reality today. Say 4 x 80GB plus a single 320GB disk to
    do a backup. That should have a reasonable starting price.

    You might also benefit from an external drive tray
    mechanism, to make inserting the backup drive easier.
    There are devices that have a small shell to hold the drive,
    which is then inserted into a drive bay. A second solution
    is to pick up a cheap SATA controller card, with an ESATA
    external port connector. That will allow transfers that are
    not limited by the performance of the cable (as would be the
    case with a USB2 or Firewire 400 enclosure for an external
    drive). It means the external enclosure needs no bridge
    board - just a power supply plus the SATA drive.

    http://store.yahoo.com/cooldrives/saingrsisadr.html

    Paul
     
    Paul, Nov 23, 2005
    #5
  6. Hi,
    Yes ... Many things can go wrong.

    As for backup ... it is a fileserver. I have a backup of my data on
    aprox. 200 DVD's. It's a fileserver for music, of which I have about
    740 GB. all files are also on DVD's. However to have redundancy, which
    is ok, if the powersupply is ok, is good, since restoring from 200
    DVD's will be rather tedious (but in case all go wrong - a
    possibility)

    Regards Leif.
     
    Leif Nordmand Andersen, Nov 26, 2005
    #6
  7. idon.wong

    idon.wong Guest

    Yah, there are alot of things to think about to make a system truly
    fault tolerant. However I'm not looking to achieve 10^-10 probability
    of failure, and will settle for 10^-5 (or whatever the real calculation
    is). Basically my goal is to build a content server mainly hosting
    movies and music. In reality it's not critical if I were to lose this
    data, however it would be a real pain to rerip everything. Hence, a
    RAID5 system with a good UPS is good enough for me.

    Anyways, here's an update on my system and the problems i'm
    encountering.

    I decided to go with a dedicated RAID card to support online expansion
    in the future.

    1x 200Gb Seagate
    3x Western Digital SATA 320GB SATA drives
    Promise FastTrak S150 SX4 with 64Mb DIMM
    Microsoft Windows XP Pro

    I use the 200Gb drive as my main O/S drive in a non-raid configuration.
    I have the latest bios, drivers and PAM for the SX4 controller. I've
    tested the memory on the controller with Promise's test utility.

    Basically, I've done the following:
    1. Create RAID5 array with the 3x320Gb
    2. Initialized for RAID 5 the array
    3. Formated a 200Gb NTFS partition

    Here's where the problems start:
    4. Copy files (about 15MB in size) from a network share to the raid
    partition.
    5. MD5 sums differ for the source and destination files.
    6. Furthermore, repeated MD5s on the same files on the RAID give
    differing results.
    7. Copy the files from the RAID to a local non-raid hard drive
    8. MD5 sums on the local drive files differ from the raid files.
    9. Copying the files AGAIN from the RAID to the local drive yields
    different MD5 sums again (differ from 8.).
    10. Copy files from local to raid drive.
    11. MD5 sums are identical, even after repeated copies.

    These results seem to indicate that network copied files cause real
    problems on the RAID5 array, that persist even after the files have
    been written. 6. and 9. indicate even read operations seem to change
    the data.

    I've contacted Promise support and eagerly await their response. I
    can't figure out what's going on.

    Cheers,
    Don
     
    idon.wong, Nov 29, 2005
    #7
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