Home > Tools of the Trade > Hardware > RAID Mirror and or Striping

RAID Mirror and or Striping

  1. Is anyone using a RAID array to backup data (mirror) your primary hd or to (stripe) span files across hds for faster access?

    I've heard the stripe route is a little less stable--so it makes me hestant. However, mirroring seems like a good idea, esp. with a 2nd hd costing ~$100.

    What's your experience, thoughts? Thanks a lot.
     
  2. stripe will make your data 1/2 as reliable - if one drive fails you lose all data

    mirror improves reliability. the mirror could protect you from downtime and data loss but tape is more reliable for data protection.

    i just went thru a hard drive failure - my power supply went out and after replacing the power supply i found my harddrive was fried also. replaced drive and still having issues with that system. tape being offline would of protected my data. luckily i had a backup on CD but couldnt fit everything on it.

    so depends on what your trying to achieve - possible lower downtime & data protection or data protection.
     
  3. So if your PS fries your main hd, it's probably fried your secondary one as well. Have you looked into using DVD for back up? & which tape drives do you like? Thanks.

    P.S. could I do something where I have the 2nd hd archive the 1st one EOD and then have it dormant at all other times?
     
  4. i would assume the 2nd drive would of been toast if i had it.

    tape/cdr/dvd doesnt matter what you use - it depends how much data you have. you want to be able to back up all data without having to change CDs/tapes/etc. i got a deal on 12/24gb dat tape drive and a bunch of tapes. one tape will hold at least 2 full backups and 2 weeks worth of incremental changes without changing the tape (just backing up data not OS or programs).

    if you have the 2nd drive go and mirror it. just realize mirroring is for reliability and uptime not a backup solution.
     
  5. Using Raid in a trading workstation is a hard to justify case.

    Using Raid 1+0 might make it better, however, the implicit notion of using RAID is also coupled with other maintenance functions done regularly and offline.

    Some of those functions would be, as mentioned, creating either a current tape or CDR/DVDR backup mirror image of the primary drives. Without that, its just like running with a catch pan, and never doing anything with what's caught in that pan.

    RAID imposes a noticable overhead upon your op-sys and for those desiring of making screaming trading machines, I'd have to ask, what are you doing that you need such dynamic backup instead of periodic backups.

    For that matter, you might also look into running with dual drives not linked what so ever, or even daisy chained in a simple network onto another physical machine over an RJ45. Couple to this a basic disk drive utility that takes frequent and timely flash backups and synchronizes them. This allows for instantaneous recovery. There are many off the shelve software products offering these features. Talk to any competent technician at your local Office Depot, CDW, Staples or other software retail chain.

    Cheers
     
  6. Couple rules of thumb - never stripe unless you're also mirroring the stripe set and never stripe unless you're using multiple physical disk controllers (not drives, actual controllers) and don't using striping just to get a larger virtual disk drive (use bound volumes instead).

    Striping is for performance and you need more than one disk controller to take proper advantage of it (you're able to do parallel data transfers which is one of the underlying ideas behind striping). Usually striping is for servers rather than desktops. Although I have seen a couple video editing setups that used striped and mirrored disks.

    Mirroring is a simple, cheap, and low impact way of creating a degree of fault tolerance and under certain conditions getting a little extra read performance out of the storage subsystem. You don't need an additional controller to mirror (unless you absolutely want maximum fault tolerance) and it'll protect you in the event of a disk crash. Note that mirroring will NOT save you from accidentally deleting or mangling files because those operations will be mirrored in realtime.

    However, if you have room in your box - there is a way to using mirroring both for ongoing fault tolerance and for backup purposes. Install three disk drives. Set disk 1 as the primary and configure an initial mirror set of disk 1 mirroring to disk 2. At the end of the week, break the mirror set and re-establish the mirror of disk 1 to disk 3. Now disk 2 is a ready to go backup. You can either then back it off to tape, CD, or DVD if you want to, or just use it as a weekly rolling backup (depends on your needs). At the end of the next week, just break the mirror and re-establish the mirror of disk 1 to disk 2. Now disk 3 is the hot backup.

    With mirroring active, if you encounter a fault or crash on your primary disk, the mirror disk will automatically take over without causing a system fault. In addition, if you're doing a lot of reading from the disk during some process, the system can use the mirror as a secondary source to read from and can overlap head seek times or if you elected to install a second controller can do parallel transfers (although the performance improvement isn't as high as a properly configured stripe set, it can be worth up to 10%).

    Mirroring causes little or no nominal performance impact. No impact if you use a RAID controller because the mirroring operation is handled by the hardware. An almost unnoticable impact if you use software mirroring except following system reboot when the mirror disk must be completely regenerated, so there's a noticable CPU and disk subsystem slow down until the regen process completes. Note that you can still do normal operations without waiting for the regen process to complete because the mirror disk is high watermarked - however you won't have a fault tolerant disk environment until the mirror is completely regenerated.
     
  7. Using Raid 5 (striping and mirroring) with 3 or more drives gives you the best of both...
     
  8. ArchAngel seems to know his stuff.

    I'm running two, 2 gig machines - each running 2 mirrored SCSI drives.
    I run Win2000 SERVER - because Win 2000 would not run "Mirror".
    I am told that XP Will run Mirror.

    I also have an "External" 36 gig SCSI that I fire up with the flip of a switch.

    I use it to back up some data , . ( and those all important MP-3 files ).
    It's esp. nice to take over to a friends house and DL all of their music.
    ( if they have a SCSI Card )

    ............................
     
  9. Arch - excellent answer.

    Bobby - that explanation is one that a non-technical person can follow.

    The net problem for you is to decide what the machine is being used for, and whether or not you need those bells and whistles. He mentioned that servers and other high performance high throughput machines needed such instantaneous backup. If you consider your processing as such then you might benefit from such an array.

    Arch mentioned that dual controller cards were mandatory, and not using the daisy chain wire linkage for HDD #2, #3, #4 off the primary. This is a technical fact that most installers usually find out about after they can't achieve any significant backup after a crash. Excellent point to recall.

    A number of mother boards provide for Raid, whereas you used to have to add a controller dedicated to providing Raid. This is an improvement, however, go over a written diagram of your proposed system before purchasing dollar one, just to make sure that the details support what you think you're achieving.

    If this is for your primary desktop or workstation which you trade upon, then you have to ask, what are you really saving on your machine that needs such instant restoration, and whether or not you can't shunt that off to another cheaper box that's not subject to virus, infection or direct connection to the Internet or otherwise.

    Again, another consideration would be the instant file duplication processes that any competent (Diskkeeper) HDD management software provides.

    good answers - Arch
     
  10. Thanks for all the EXCELLENT replies!
     
  11. As long as you you have a solid internet connection and computer, you will be just fine. Technology has improved over the years where you basically just need abit more ram and a decent processor speed. I used to invest in robust computers, and now i am hardly utilizing it. My advice, dont go crazy... but in the end, it depends on what kind of software you are using. oh, go and get yourself a nice 2-4port video card if you dont have one.
     
  12. Actually Raid 5 is not striping and mirroring (that's Raid 0+1, although there is also a Raid 10 configuration that's an alternative way of doing fault tolerant striping).

    Raid 5 is striping with distributed parity (ECC) blocks - not mirroring (a hardware implemented Raid 3 config is often better than Raid 5).
     
  13. Make sure that the use is appropriate. What is the purpose of your Raid setup? And please tell me that you are doing this with real networking (hopefully Novell) software. You might be setting yourself up for more troubles than you understand right now. Raid, mirrored, stripped drives? Those are heavy user setups for just trading/word processing platforms. Quake and Doom aren't that serious! :D
     
  14. RELIABILITY.......is the Point.

    Whether you pinch pennies or throw Bucks at it to achieve it.

    A down week can easily cost you the price of a new system or two.

    Not to mention the Frustration Factor that comes with Losing Data.
     
  15. No, it's just a network of one. Thanks for your advice.
     
  16. OK, but stripping in this instance is not the answer. According to the patient, there is only one un-networked computer. That is not a good "Tech" advised method to take care of the issue of "reliability." That is too broad a term to plan a solution like stripping for. Saving data can be easily achieved by simply adding a 10 gig hd for "data only." Simple, concise, cheap insurance. There are a lot of other things that could fill the bill if you know what the real underlying issue is. :)
     
  17. The computation as to whether you even need a RAID configuration should be based upon how much money you could lose from non-availability of your systems per unit time. In a one person / one computer office you probably could get away with just using IDE drives and a tape backup ...

    Do the calculation ...... To restore the OS and application software and configurations from tape might take an hour for most users - excluding any large amount of data (100's GBytes). If you simply bought two or four 80 GByte IDE disks at about 120.00 or so each you would be far cheaper than the typical RAID Array and it is much simpler to simply replicate (out of the box functionality in Windows Servers) data between disks, or even just write a script to copy active data each day or each hour etc. IDE is fast enough for most uses.

    So, if you are down for an hour say, did you lose more than than the 1-2K for the minimum RAID array ? How often can a failure like this be this be expected ?

    For example, We have IDE drives that have been running 24 hours a day every day with fairly heavy IO and they typically do
    something like 2 years between failures .....

    So the moral is dont overspend unless you know that an IDE system wont work due to access speed requirements or loss of business requirements dictating a fault tolerant configuration: fault tolerance costs $ in terms of equipment and personnel.
     
  18. Excellent deciphering of the issue here. Really makes a tech smile when the basic issue can be addressed like this. :)

    Another solution would be to go to a light/medium weight server machine and turn it into a workstation. Base the setup on SCSI drives with hot swap capabilities. You've now also opened yourself up for advantages like multiple processors, massive amounts of RAM, multiple hot swap power supplies, etc.

    And if you are prudent, you can do all this at a reasonable cost. Especially if you look to corporate equipment coming off lease. It is usually very well taken care of. And generally not abused as companies generally maintain their equipment (like servers) extremely well.

    I couldn't have said it better. I second that motion! :D
     
  19. Thanks again guys for the advice. A system builder out here in LA recommended a serverboard system w/ RAID array (stripe & mirror). I talked with a good computer shop (PC Club) and they split on this approach.

    Your responses have clearly removed any questions from my mind. RAID is too much for my setup (XP Pro, TS6/7, TradeStationFutures, TWS, thinkorswim's front end, Excel, Access (sometimes), Word (sometimes), IE, OutlookExpress).

    I'll probably be sucking it up until the new P4's with the 800Mhz buses are released in a few months and then go some P4 route.
     
  20. AS Windows 2000 Workstation, XP Pro (and Home ed.) don't support native Raid software as Win 2000 Server, you will have to choose XP dotnet edition (server ed. of XP available since few weeks) for do that. But the both can support Raid hardware controller or onboard Raid controller without problem.
     
  21. Good choice. I don't think that the softwares you have addressed will really show any major pickups in abilities/speeds for your uses though. But it will be a nice machine I'm sure. Good luck and happy trading! :)
     
  22. Diskkeeper comes to mind, but there are a number of other products, as well as those products that are now wrapped in under Win2000 Server as features.
     
  23. The 800Mhz FSB's (front side bus) along with QPB support will show a radical speed improvement across the board on all applications being run, both on laptops (when the equivalent chipsets are released) and on desktops.

    Under that basis, the background tasks of parallel data support (as described through multiple means earlier) will have a far smaller overall impact upon your processing speed and speed of your applications.

    You mentioned a healthy combination of applications, inclusive of TOS Option's package. Who do you use for Direct Access and are you a Prop or Retail (IUDM - if you don't mind)?
     
  24. What product will make a backup image of a hard disk onto a DVDR? Never heard of such a thing.
     
  25. Dont run an OS based software RAID. If you cant boot up into the system, then you are locked out of your disk.

    Run the Promise RAID controller and 2 hard disks for mirroring. Its very simple and the OS overhead is no big deal for anything resembling current cpus.

    If you absoluletly want NO additional CPU load, run the 3Ware controller which has its own on board processor.

    Mirror RAIDs are easy and IMO should be standard for business for developer workstations.
     
  26. Backup/recovery software usually comes with a CDRW/DVDR-RW drive for that, e.g., the HP CDRWs ship with an HP utility that will image your hard drives to CDs and create 4 bootable floppies. If there's a disaster, you can boot from the floppies and restore the complete disk config from the CDs.
     
  27. I'm just a regular person slowly getting more into trading and hoping to make a living at it eventually. As for direct access, I've got three accounts. Interactive Brokers' Trader Workstation, TradeStation's TS6 (not really direct access for futures), thinkorswim's frontend (for options). Sorry, I'm still a little new to all this, what does IUDM mean?
     
  28. IUDM - if you don't mind.... (me asking)

    I actually quoted it.
     
  29. :eek: :)
     
  30. Bobby,

    Its rare that this many persons with in depth technical experience, as exhibited here in, will have the inclination or the time to contribute to these threads, let alone take the time to clearly explain their thoughts.

    Normally amongst us Tech's we speak in acronym soup and quite fast at that. Ever see "Alias"?, Marshall is an excellent example of that.

    This time, we got over four diffent clarifications and explanations of Raid, Usage of Raid, Practical implementations of such, Recommendations of pseudo-Raid configurations, normal-Raid configurations and alternate-Raid configurations (software based).

    Now if we could only explain how to place a trade, then.....



    :p
     
  31. Yup, much applause to all of you! :) :) :)
     
  32. my personal preferences:

    don't use a RAID system unless you specifically have a RAID hardware subsystem. Software based RAID in my opinion really sucks.

    I think raid for a workstation is overkill, it is better to get one hotswap drive tray, image your system, build the image on your other hotswap drive. If your hard drive fails, just swap the drives and reboot.
     
  33. interesting thread, agree re useful tech tips, thx all. ...

    Questions:

    I just got a promise tx2000 fasttrack raid hardware controller w/disk bays...getting ready to install it one of these days ...

    I have 3 western digital 120 gig harddrives, so making sure the right process is:

    a) backup the main boot drive (HD 1) data to HD3 and put in a safe place just in case Before I try all of this stuff ..

    b) install/setup the raid card per its instructions, using HD1 and having it mirror over to HD2

    c) and every now and then, swap out HD3 like Arch said above, eg weekly for backing up ..


    sound ok so far?

    q: anyone know if my roxio goback software will/won't work with a h/w raid promise setup like this? or anything else I should know before I get under the hood o the pc again?

    appreciate it ..



    ken


    in other h/w news, fwiw:

    a) I found my matrox parhelia agp card Will work with a lowend nvidia pci card I got this last weekend (yay) for 4 monitors on my p4 m/b with the intel 850e chipset.. I'll get a couple more and see how many I can pack in the pci bus before it chokes.. hopefully all 6 mons..

    b) reminder from the pc guy that a virused mirror just means twice the virus fun lol, no protection against those from mirrors

    c) the intel p4 m/b still randomly reboots every now and then when I close an app simultaneously, when I have a few open, frustrating, though everything (mem/pwr) is all set up right, and 6 various antivirus/antitrojan progs find no bugs, plenty o mem..and it frequently gives 'boot drive failure' when rebooting, though all's fine with the HD and ide config. so I have to go into bios and change hard drive preboot delay to various settings to get it to 'find it' on the ide, sigh .... ideas?

    seem just this dang intel m/b... I'm not getting those (or gigabyte) anymore, sticking w/asus/tyan for future boards..