If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
What are the advantages of RAID setup?
Please help educate me.
I am considering setting up a RAID system on my P4 computer. I am anticipating that the advantage is mostly speed of access increase for a striping setup. What are the pros/cons of such a system? Can anyone give me a target figure on access speed increase? I am currently running ATA100 with a 7200rpm, 8Mb HD. TIA, Rich |
#2
|
|||
|
|||
"Rich" wrote in message
... Please help educate me. I am considering setting up a RAID system on my P4 computer. I am anticipating that the advantage is mostly speed of access increase for a striping setup. What are the pros/cons of such a system? Can anyone give me a target figure on access speed increase? I am currently running ATA100 with a 7200rpm, 8Mb HD. TIA, Rich Pro: can be somewhat faster. Con: far less reliable: one slight error on either drive and you've effectively lost the content on both drives. Personally, given the speed and capacity and price of modern IDE drives I'd far rather have mirrored RAID and forego the possible speed increase in favor of the reliability. Face it, with the size of modern drives it is becoming increasingly impossible to do decent backups. In the old days (10 years ago?) I could plug a tape into my machine every night, start a backup and be done with it. Now, how does one affordably back up a 250Gb drive so easily and cheaply? Just my $0.02 of course... -- John McGaw [Knoxville, TN, USA] Return address will not work. Please reply in group or through my website: http://johnmcgaw.com |
#3
|
|||
|
|||
John McGaw wrote:
"Rich" wrote in message Please help educate me. I am considering setting up a RAID system on my P4 computer. I am anticipating that the advantage is mostly speed of access increase for a striping setup. What are the pros/cons of such a system? Can anyone give me a target figure on access speed increase? I am currently running ATA100 with a 7200rpm, 8Mb HD. Pro: can be somewhat faster. Con: far less reliable: one slight error on either drive and you've effectively lost the content on both drives. Personally, given the speed and capacity and price of modern IDE drives I'd far rather have mirrored RAID and forego the possible speed increase in favor of the reliability. Face it, with the size of modern drives it is becoming increasingly impossible to do decent backups. In the old days (10 years ago?) I could plug a tape into my machine every night, start a backup and be done with it. Now, how does one affordably back up a 250Gb drive so easily and cheaply? One installs a second drive and clones the first with XXCOPY (See xxcopy.com). Any further backups are automatically incremental, and go much faster. Then, WHEN the first drive fails, you have a copy of everything. Your backup is probably done within 15 minutes, and may even be done in the background. For Linux, you will have to build the equivalent yourself as far as I know. -- Chuck F ) ) Available for consulting/temporary embedded and systems. http://cbfalconer.home.att.net USE worldnet address! |
#4
|
|||
|
|||
"John McGaw" said in :
Pro: can be somewhat faster. I suppose if you went to all the bother of setting up RAID but then foolishly put the 2 hard drives on the same controller then, yes, the bandwidth available for both drives in aggregate would be only nominally better. However, if you're going to go to the effort of using RAID, you'll want to put the drives on separate controllers (i.e., on different IDE or SATA ports). Then you'll get a near doubling of bandwidth (having the 8MB buffered drives will also help). Con: far less reliable: one slight error on either drive and you've effectively lost the content on both drives. Which proves that for a server you don't want to use this configuration. For home use, and if you have another drive (internal or external) or use CD-R[W] (although you'll probably want to get a DVD-+RW drive) then striping is great. ... I'd far rather have mirrored RAID and forego the possible speed increase in favor of the reliability. Face it, with the size of modern drives it is becoming increasingly impossible to do decent backups. Mirroring a drive is *not* backing it up. You are providing disaster recovery in case the primary drive goes bad. The mirrored drive has the same contents as the primary drive, so where are your backups? They aren't on your mirrored drive. You are "backing up" your hardware when using a mirrored drive. You are NOT backup up your files in the sense that you have historical copies from which you can restore. Rich, If you really want to go to the bother of using RAID to get a lot better bandwidth (i.e., effective speed) for your drives, and if this is for personal use where the box is not critical and there is no requirement that it always be up (or be able to be brought back up under an hour), then RAID 0 is fine. Just be sure the 2 drives are very similar. Best to get 2 of the same brand and model. However, as John mentions, you are interlacing (striping) the data for a file across the 2 drives (unless the file is smaller than the stripe size) so any file error, surface defect, or other error in the file renders that file corrupted. Corrupting a file does not corrupt the entire striped volume anymore than a corrupted file would screw over your file system now. If you RAID, you *must* consider how you are going to backup your data ... unless you consider your data absolutely worthless (and also your time absolutely worthless to reinstall the OS or applications and redo all the configurations and customizations). With a DVD-+RW drive, you get a reasonably capacity on each disc. You get get pretty good storage capacity on some tape formats, like DLT, but tape is excrutiatingly slow and all commands are serial. You don't mention what is the size of your current hard drive (the 8MB you mention is the buffer size). If you currently have a 120GB drive, get another 120GB drive (same brand and model if possible). That will give you 240GB striped RAID at twice the bandwidth of a single drive. But consider that you'll have to buy another 120 GB, or bigger, on which to store the compressed backups or to save disk images unless you want to swap a lot of CD/DVD discs or tapes. For personal use, and although it sounds great to have the potential of double the bandwidth for drive throughput, few end-user applications would sustain such a load on the drives. Unless for some reason your "personal" computer is running an SQL database with huge-sized multiple db files that are being concurrently accessed by a hundred users, or more, or some such high disk usage setup, you won't get hardly any noticeable speedup from using RAID when writing your letter in Word, browsing with IE, or posting in newsgroups. You must actually have something that will put such a huge I/O load on your system to make RAID worthwhile. -- __________________________________________________ __________ *** Post replies to newsgroup. E-mail is not accepted. *** __________________________________________________ __________ |
#5
|
|||
|
|||
"*Vanguard*" wrote in message
... "John McGaw" said in : snip... ... I'd far rather have mirrored RAID and forego the possible speed increase in favor of the reliability. Face it, with the size of modern drives it is becoming increasingly impossible to do decent backups. Mirroring a drive is *not* backing it up. You are providing disaster recovery in case the primary drive goes bad. The mirrored drive has the same contents as the primary drive, so where are your backups? They aren't on your mirrored drive. You are "backing up" your hardware when using a mirrored drive. You are NOT backup up your files in the sense that you have historical copies from which you can restore. Rich, If you really want to go to the bother of using RAID to get a lot better bandwidth (i.e., effective speed) for your drives, and if this is for personal use where the box is not critical and there is no requirement that it always be up (or be able to be brought back up under an hour), then RAID 0 is fine. Just be sure the 2 drives are very similar. Best to get 2 of the same brand and model. However, as John mentions, you are interlacing (striping) the data for a file across the 2 drives (unless the file is smaller than the stripe size) so any file error, surface defect, or other error in the file renders that file corrupted. Corrupting a file does not corrupt the entire striped volume anymore than a corrupted file would screw over your file system now. If you RAID, you *must* consider how you are going to backup your data ... unless you consider your data absolutely worthless (and also your time absolutely worthless to reinstall the OS or applications and redo all the configurations and customizations). With a DVD-+RW drive, you get a reasonably capacity on each disc. You get get pretty good storage capacity on some tape formats, like DLT, but tape is excrutiatingly slow and all commands are serial. You don't mention what is the size of your current hard drive (the 8MB you mention is the buffer size). If you currently have a 120GB drive, get another 120GB drive (same brand and model if possible). That will give you 240GB striped RAID at twice the bandwidth of a single drive. But consider that you'll have to buy another 120 GB, or bigger, on which to store the compressed backups or to save disk images unless you want to swap a lot of CD/DVD discs or tapes. For personal use, and although it sounds great to have the potential of double the bandwidth for drive throughput, few end-user applications would sustain such a load on the drives. Unless for some reason your "personal" computer is running an SQL database with huge-sized multiple db files that are being concurrently accessed by a hundred users, or more, or some such high disk usage setup, you won't get hardly any noticeable speedup from using RAID when writing your letter in Word, browsing with IE, or posting in newsgroups. You must actually have something that will put such a huge I/O load on your system to make RAID worthwhile. -- __________________________________________________ __________ *** Post replies to newsgroup. E-mail is not accepted. *** __________________________________________________ __________ You will notice that I didn't write that having mirrored raid is the same as having a backup. It is simply more reliable than having a single drive and FAR more reliable than using a striped array. The difficulty of doing a backup is the reason I would prefer mirrored over striped when the data involved has any value at all. If a backup is to be of any real use it must be current. And the backup ideally should be placed off-site. And there needs to be a historical record going back at least three (in my experience anyway) generations if not further. And the backup has to be dead reliable. And it must be essentially hands off once it starts unless it is impossibly quick. This makes DVD-RWs seem impossibly small for the task and juggling even a handful of discs is anything but quick or hands off. And having three sets of portable hard disks seems impossibly expensive. What the world needs is a good cheap reliable tape system that can hold 1/2 terabyte! -- John McGaw [Knoxville, TN, USA] Return address will not work. Please reply in group or through my website: http://johnmcgaw.com |
#6
|
|||
|
|||
Rather than get into why data backups are good and why hardware backup is
good, we first need to find out if Rich even does any backups now. If he doesn't backup now, he doesn't care about his data or time. His data is of no value to him, or it can be rebuilt, or recovered somewhere from elsewhere. His time is of no value to him to reinstall the operating system, reinstall his applications, and to configure and customize it all again. Talking about RAID 1 to someone who doesn't do backups now is a fruitless argument. They aren't backing up now. They won't be backing up later. Your point is that adding more drives in a striped RAID 0 set will reduce reliability. Yes, it will. If the MTBF (mean time between failures) for a hard drive was 3 years and you add another in the same RAID 0 set then you get 1.5 years for MTBF. But a non-RAIDed drive with 3 years MTBF could still tomorrow. If Rich isn't backing up now, he doesn't care about data or hardware recovery. So RAID 1 won't be an option for him. I also suspect if Rich is asking about RAID 0 and never mentioned RAID 5 then his RAID controller only supports RAID 0 and 1 (and maybe 0+1). It's likely he is looking at using an onboard RAID controller on his motherboard. If Rich had the availability of RAID 5, and if he could afford 2 more drives instead of just one (since he isn't going to spend any money on backup drives and media), then he should go with RAID 5 with 3 drives. It comes down to waiting for a response from Rich to find out if he does backups now and, if so, what backup device he has or will get. If he doesn't backup now, does he want to spend the money on yet another drive to only have it used as a backup with mirroring in RAID 1? Not likely. He doesn't do backups! If he is willing to spend the extra money to incorporate backup (data or hardware), will he spend it on the second drive and use mirroring in RAID 1 (and still not have the speed advantage of striping), or would he rather spend it on a tape or DVD-+RW drive so he has the advantage of removable media that can be used in another drive (so he doesn't have to worry about the drive going bad and becoming unusable for restoring his system) and even restor to another host? RAID 1 is used to keep the host running or get it back up quick, not for backing up your files. RAID 1 is for hardware recovery, not data recovery. Or does Rich still not bother with backing up his computer and use that same money that would otherwise be for a backup device (mirrored drive, tape drive, CD-RW drive, DVD-+RW drive, or external hard drive) and use it for a 3rd drive so he has 3 drives and can use RAID 5 which offers the speed advantage of striping along with hardware recovery? Instead of spending money on backup hardware whether for data or hardware recovery which he does not do presently, he instead spends it on the 3rd drive which gives him the speedup plus covers his butt with some hardware recovery. He still has no data backups (but he didn't have them before, either), he gets his need for speed satisfied, and he gets some hardware protection despite his lack of enthusiasm for backing up his data. I can promote data backups until I'm blue in the face, but if the user doesn't do it now then it is very unlikely they will employ it later. In that case, RAID 1 is not an option to that user. RAID 0 is a more appropriate choice *if* they really have a need for the increased *potential* bandwidth it can offer. Yes, RAID 0 has reduced reliability but then the user doesn't care because they're not doing backups now. You don't rely on a higher MTBF to protect your data - if it's worth protecting. A RAID 1 setup that has an MTBF of 1.5 years could run a decade before a hardware fault killed that RAID set. A non-RAID single-channel drive (his current setup) with an MTBF of 10 years could die tomorrow. A RAID 1 set with 2 drives each having an MTBF of 10 years could die tomorrow because static or a surge fried both drives, or the single controller got fried and has to be replaced (unless you really get pricey to employ duplexing), or the CPU fried, or whatever occurs within the same host in which the mirrored drive coexists with the primary drive. The point is that backups which are on separate media that is removable from the host and usable on replacement drives or even in substitute hosts is how you backup your data. RAID 1 is how you provide disaster recovery of your hardware. Unless Rich is using his computer as a server (and used in a network where other users need it) then there's little point in providing disaster recovery except based on your own personal needs and budget. Alas, when talking to newsgroup posters that inquire how to recover a file that has been thoroughly deleted and telling them to use their backups, the response is akin to deer caught in headlights: you get a vacant stare implying "Backups?", a roll of the eyes, and then "Um, any other suggestions?". No RAID setup supplants the need for a backup scheme. Don't confuse hardware disaster recovery with data recovery. RAID 0 gives you a *potential* speed increase with the reduction in *probable* failure time. RAID 1 gives you disaster recovery provided only the drive went bad and not the controller, motherboard, CPU, memory, or other common hardware, but you get no speedup. RAID 5 gives you the speedup along with the hardware disaster recovery. None provide you with backups. It is unfortunate that "backup" can be used to discuss saving a historical image of your files on removable media or to discuss how to maintain your hardware presence. Backing up your data is not the same as backing up your hardware. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Desperately need help installing OS with RAID on an Intel mobo | Nate | General | 10 | January 1st 04 07:17 PM |
Incompatible RAID controller? | @drian | General | 1 | November 9th 03 07:38 PM |
help with motherboard choice | S.Boardman | General | 30 | October 20th 03 10:23 PM |
RAID 0 setup questions | Ronald | General | 2 | September 1st 03 01:40 AM |
help. ga-7vrxp raid trouble, compatability and warning | todd elliott | General | 0 | July 17th 03 06:50 PM |