Converting from Raid 0 to Raid 5

peanutympeanutym
edited March 2005 in Hardware
I am useing teh supermicro mobo X5DPL-TGM on this board it has a built in SATA raid controller that will control up to 8 SATA drives. i loaded the machine with 2 250 and did a raid 1 (mirror) is there a way in the future to add 1-6 more drives and convert the raid to raid 5 w/o losing any of the information?

i say 1-6 cause if it takes 1 thats fine but if it takes all 6 i would like to know that also. i can forsee myself in the future want more than just the 250 gig and would like to get it up to 1.5 tb later on, but would like to know if i need to remake the raid and if i would need to backup my information.

Also i just installed all of the stuff on this server, if i cant convert later on would it just be better/easier to buy another sata 250 and make it raid 5 now with the 3 drives, and just reload it all? i would assume so so that i didnt have to worry with backup later on of all my data.

If i do that i would be able to add the other 5 drives seemlessly afterwards correct? since the raid controller would just see the drive and i would tell it to add it to the array.

thanks for your time.

Comments

  • TexTex Dallas/Ft. Worth
    edited March 2005
    yes you need to backup your data. When you create the raid-5 array you lose any data on the drives before.

    The write speeds are horrible on raid-5 did you realize that? I mean like on a par with a single ide drive made 5 years ago if you use a controller like that?

    Consider raid-10 if performance is important.

    Let me know if I can help further.

    Tex
  • peanutympeanutym
    edited March 2005
    i would like preformance but its not top of the list i am more looking at the storage but when transfering the information i do need the preformance out of it also, you said raid 10, any links on a explination of how it works, preformance, storage compasity? like in raid 5 you lose 1/4 of the space or whatever just wondering on that.

    if you have any handy of a explination of how to set it up and those kinda things that would be greatly appreciated.
  • TexTex Dallas/Ft. Worth
    edited March 2005
    Raid-5 doesnt always lose 1/4. With three drives for example you lose one. Thats 1/3.

    On raid 5 to make one write it has to read from the other drives to get the parity info. So in a three drive setup it reads from both other drives between every write and therefore no two writes are ever sequeential as the heads have to move and do reads on every drive in between. With ide the access times suck anyway and the key to performance is reading and writing sequential so ide raid-5 suxs three times worse then scsi raid-5.

    Picture raid-10 as raid-0 drives mirrored. So you get speed and redundancy. You lose half the space. But for instance a single fast ide drive now writes at 50 to 60,000 STR and you may get 5 to 10,000 writes raid-5 on that controller. You can burn cd's faster then that.

    Don't use raid-5 with that controller if your going to write to it much. Its one thing to store casual info thats written once and then mostly just read. Like MP3's etc.. Not an OS etc...

    Te
  • peanutympeanutym
    edited March 2005
    yea this will be something that is wrote to every day by multiple people. in essense this is going to be a ftp server that people will upload to mostly.

    so your saying i should do raid 10 for that, which i would still lose 1/2 my space and i would have to set it up as 2 drives raid 0 and 2 drives raid 0 then make them raid 10 together? i dont have time to research it all right this second is why im asking so many questions, but ill be able to tonight and not be so noob about it.

    but also if its a ftp server with say 5 people uploading to me at the same time. with raid 5 more than likely, the ftp sessions would be waiting on the drives to write the info? if that is the case then i want performance over space.

    let me know what you think please
  • TexTex Dallas/Ft. Worth
    edited March 2005
    HPT may also call it raid 0+1. Or 1+0 They are all basicaly the same thing. You are either making two raid-1 ararys into a raid-0 or mirroring two raid-0. Half a dozen of one or six of the other (grin).

    I personally have no use for raid-5 other then perhaps as a mp3 server or to hold my install iso's etc..

    Tex
  • peanutympeanutym
    edited March 2005
    so what would you recommend then for my current setup? also do you think that i would notice the performance with raid 5 doing FTP transfers? like i said before would be mostly uploading to me, so i would be intaking alot of info at once.
  • TexTex Dallas/Ft. Worth
    edited March 2005
    Do you think you would notice if instead of using new state of the art sata drives that instead you used a single old 4gb ata33 drive made 7 or 8 years ago?

    I would notice when doing list directory on the files. And you plan to have multiple people at once possibly ftp'ing to the drives?

    Is this for a website? Can you be selling them something while they wait for the transfer to complete maybe? As you got lots of time to be throwing comercials or popups at the poor shmoo's if the ftp's they are doing are of any size to transfer.

    Not sure how else to lay it out for ya. With raid-5 on maybe 5 total disks you might get 5,000 or so on your write speed. I managed that with 8 scsi drives and the onboard cpu and cache turned off on a high end hardware raid controller. So consider that ballpark anyway. A single new 250gb sata drive will hit 55 to 60,000 on writes not raided.

    A highend 3ware controller in a 64bit slot would score better.

    With raid-5 the faster the onboard cpu is and the larger the cache in general the faster raid-5 will work. This isnt a absolute as the caching algo. used highly impacts performance and some controllers are much faster then others.
    I have not used the new raidcore controllers but in general if I was running raid-5 on ide/sata I would be looking at a high end 3ware card. But I demand performance. I have a pretty nice network with multiple 64bit servers ona gigabit network in my house. I back up one server to another regularly. I run scsi raid backed by single large ide drives. All my data gets backed up regularly onto other local disks as well as other servers so its redundant to the max.

    Four drives in raid 10 will hit close to 100,000 on the writes. Thats at least ballpark. May hit 80,000 may hit 110,000.

    5 thousand versus 100 thousand? Twenty times as fast.... You reckon you can tell the differance? Only you know the answer to that one. Go copy half a gb of something and time it with a stop watch. Then multiply times twenty. And that times "20" is a single user so the copy is sequential. When you get the heads jacking back and forth to differant spots with multiple copies at once you may need to multiply times a hundred or more.

    Will you be able to tell the differance?

    I bet you can.

    Tex
  • peanutympeanutym
    edited March 2005
    lol thanks, now to find out if my board will support raid 1+0
  • TexTex Dallas/Ft. Worth
    edited March 2005
    most the even lowend non hardware raid controllers like the promise and HPT will suipport raid 0+1 or 1+0.

    Remember most the lowend cards are just software raid not hardware. To be a hardware raid controller they need an onboard cpu and cache generaly speaking. The cpu handles the stripping and the cache buffers the I-O.

    You could also consider a two stage setup where they actively ftp to small fast disks. Even scsi and then they get archived off to raid-5 at night. So everyone can download from the archived raid-5 but upload to really fast scsi drives or raided scsi drives etc...

    Lots of ways to skin this cat. Your only critical I-O time is uploading the ftp. After that it could be easily archived to a raid-5 where its just read mostly.

    Tex
Sign In or Register to comment.