RAID!!! Is it a a good idea for PCs?

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  • KwitkoKwitko Sheriff of Banning (Retired) By the thing near the stuff Icrontian
    edited March 2008
    Nickboxer7 wrote:
    But I was wondering what you guys thought about 0+1 or 10 for a storage server? I was going to build one up and planned on doing striping for performance and mirroring for protection.

    We use RAID 10 here at work for our SQL Server. I think it's the best balance between performance and security, especially if you're doing a lot of reads/writes. If your storage server is going to primarily serve files and not write so much, you're probably better off with RAID 5. Great redundancy and read speeds.
  • Mt_GoatMt_Goat Head Cheezy Knob Pflugerville (north of Austin) Icrontian
    edited April 2008
    Good thread kryyst. I have been preaching this for some time and also have been trying to explain why it doesn't work for home use and what is a better use of multiple drives for a performance home system for some time now.
    rapture wrote:
    Tex is going to **** the bed when he sees this.
    Tex is the one who made me see the light of how to get better perfomance from a home system with out using RAID 0. Tex knows that, as mentioned, hardware RAID over software RAID and dedicated controller cards over motherboard imbedded controllers is far superior for those who do need or wish to use it.

    The main thing with RAID 0 is that it is only good for the transfer of large files and not the small file loads and transfers used in everyday home useage including games! It also makes no sense to transfer a large file with a single RAID 0 from one location to another since the heads of anything but a good SCSI drive are simply not capable of the load. If someone wants to use a RAID 0 for say gaming where they load all the files to it from the install disc. that is all that RAID 0 array is going to really be good for, except maybe storing movie files that will need to be backed up on a separate drive. the file sizes involved in everyday useage, especially system operations is so small that tranfer speed does not really come into play by itself. This is where access times are much more critical. and NO RAID ARRAY WILL INCREASE THER ACCESS TIMES AS IT IS A MECHANICAL FUNCTION OF THE DRIVE ITSELF!

    A dedicated RAID controller card does 2 things that a motherboard embedded controller (all motherboard embedded controllers are software RAID) do not do. 1. They use their own processor dedicated to nothing but running that RAID array with no hit on main system performance since it isn't borrowing CPU power from the main system. 2. They all use their own memory to run the controller with no hit on main system memory. The onboard RAID solutions DO NOT have their own processor or memory. This is essentially what makes them all software as all they are composed of is a control chip, firmware and software to run them. I have seen an average hit on CPU performance and memory of 15% on the mobo software controllers. How could anyone think for a second that an additional 10 to 20 dollars for onboard RAID come close tom competing with a controller card that costs hundreds of dollars!!!

    This brings me to what I have learned first hand from Tex, who is our local master guru of drive system performance. I use the fastest access time hard drive I can find that is relatively small for nothing but the OS and anything associated with it. Then I use a separate HD for my programs and apps only. Finally I put all my storage on a separate HD and back that up regularly to an external HD. This drive system runs so smooth and access is great beacause the heads that run the HD are never trying to do 2 different tasks at the same time. It just runs like hot butter! :)
  • edited August 2008
    Redundacy, is the reason I chose to install a RAID (1) on my new system. I have had hard drives fail in the past and I didn't want to be bothered by another failure. Having a second hard drive with the exact copy of my primary hard drive without having to manually copy important files seemed like an ideal solution.

    Yes, I'm a novice (hence, Dummie)when it comes to RAID in's and out's but I don't think the problem has to do with RAID itself. Setting up a RAID on my system was quite easy. I think the problem with RAID is with the lack of explanation of problems you can encounter after you set up your RAID configuration. For example, I just updated my BIOS. After I updated my BIOS I could not boot into Windows using my RAID configuration but I could boot Windows using either hard drive separately. The reason for this was because after my BIOS update I started Windows without first telling my new BIOS that I was running a RAID set-up. Unfortunately, there are no warnings about this from any motherboard vendor and no where have I seen anyone talk about or explain what can happen to your RAID set-up after a BIOS update.

    I still think RAID (1) is a great solution but it just needs to be explained better to the not so informed.

    Cheers,
  • kryystkryyst Ontario, Canada
    edited August 2008
    The thing is that you could be getting better redundancy without using raid. Have your primary drive as normal then have it run scheduled backups to your second drive. Simple as that you then have full redundancy and easy portability should your system crash. Pull out the hdd with the backups on it and plop it into the new system and recover your backup.

    In your case the issue is that if your RAID fails, sure you can use the drives independently since it's RAID 1. But your know further ahead and you've just got the complication of having to deal with repairing the RAID should something go wrong, like it did in your case.

    Also keep in mind that RAID's are dumb. So if your data starts to get corrupted it'll mirror that corruption. Now doing a scheduled backup isn't immune to that but keep this in mind, most backup software will tell you if it had trouble backing up a file and create a report and if you are doing rotational backups, which you can usually have at least 2 since the backups are compressed you should have a good one. With RAID on the other hand if your system gets corrupted and goes BSOD then comes back with system32 style errors RAID won't save you and you'll have to do a full repair. A backed up system though means you won't loose any data and you can recover from your good backup.
  • foolkillerfoolkiller Ontario
    edited February 2009
    I think the title of this says it all. If you think a RAID array is the ultimate way to keep your data while being lazy, you're going to end up with an unpleasant surprise. I'm going to go into a bit of a story, as well as some details. I'll pop the story in first, because stories are fun, especially the horror kind.

    I've been running RAID arrays for a very long time. Back when I owned a Netfinity 5500 M20, I had two seperate arrays. A 6x18GB 10K RPM SCSI Raid 5 Array, and a 7x74GB Raid 5 Array. While I had lots of space, the antique drives I was running, weren't quite up to par, so I decided it was time to upgrade to a new server.

    First I bought myself a couple 3ware cards (by accident I ordered the wrong one TWICE for a customer, but oh well.)

    I tossed them in and got myself setup with a 4x500GB array in my new (to me) Dual Xeon 2.4 Ghz server. Everything worked like a champ. Eventually though, I started to need more space for all my junk. I ended up picking up 4 Seagate 1TB drives and this is where my horrors began.

    First off, I backed up all my data to one of the 1TB drives. Pulled the 500GB drives and setup a new array using 3 of the 1TB drives. After a day, I wondered what the hell was going on and heard the great clickety click of doom. After figuring out which drive it was, I pulled it, transferred the data off the extra disk to some old 250GB drives, and then rebuilt the array in a few hours using the 3 disks. Wow I thought, I have 2TB of data, that's awesome. So I proceeded to put all my data back on there, and everything was fine.

    Eventually I picked up another disk, and migrated the array to 3TB in size. The big thing I forgot to do, was add support in my kernel so that I could access and use >2TB drives. Needless to say, I had to do a reboot, and when the system came back up, my xfs filesystem went away, far far away. In my stupidity, I ran a chkdsk on it, obliterating most of my data in the process.

    After several hours of screwing around with my system, I eventually figured out there are TWO spots in the kernel that you need to enable >2TB disks at. I paid for this is music and video data, while having a spare backup of all my settings just by chance (LUCKY)

    This is a good description of why RAID isn't a backup solution, it doesn't take all that much to kill the filesystem on it. A good virus or ID ten T error will do it, as in my case.

    While there are a bunch of different raid levels, I'm going to touch on some of the basic ones

    RAID 0: Increases your transfer rates, IOs and capacity. The 0 stands for how many files you get back if something goes wrong.

    RAID 1: Increases your transfer rates on some controllers for reads, slightly slower writes, redundancy. Mostly run in pairs, if you lose a single drive, you won't lose all your data, however a bad sector might ruin your day still.

    RAID 2,3,4: Obsolete nuff said.

    RAID 5: Increases your transfer rates during reads, slow writes, redundancy for a single disk only. Must be run in 3 or more units. If one drive fails, you can rebuild. IF 2 FAIL, CRY. Alot of people don't realize that two failures in a RAID 5 array will mean the end of any data on it. Same applies as Raid 1 for bad sectors and such.

    RAID generally is not the best idea for home users. Too many people think it is magic and is going to give them 200MB/sec read speeds and such. There is always a tradeoff. Even with $400 RAID cards, I only see about 100MB/s reads, writes are much much slower. While I can load my games really fast, installing them takes twice as long as a single drive.

    Anyways, I've done enough storytelling and ranting. I can put it simply. If you think RAID is going to save all your data, eventually you are going to lose data. There is no substitute for backing up anything critical, period.

    Just my 2 cents.
  • LeonardoLeonardo Wake up and smell the glaciers Eagle River, Alaska Icrontian
    edited February 2009
    Thanks for taking the time for your input. There is actually a fairly large camp here at Icrontic of former RAID users, including me. In my opinion, at the desktop level, RAID is a bigger liability than benefit.

    People, if you want data security, back up or image to an EXTERNAL hard drive. Unplug the drive when not in use. If even greater security is needed, store the external drive at a location separate from your computer. This is much better backup security than any RAID setup. If you aren't serving large volumes of data on a continual basis, RAID is a toy. Nothing wrong with toys, as long as you understand the risks.
  • edited December 2009
    I've gotta say this place seems to get more "I have a raid problem" posts than anywhere else. Thanks for edumekating the interwebs.
  • photodudephotodude Salt Lake, Utah Member
    edited December 2009
    kryyst wrote:
    You want a speed boost take the money you are wasting on redundant drives, buy more ram, put in a better graphics card, don't bother with putting the drive in a raid just use it for backups. Whatever you do, there are much better ways to make a system better then spending it on a raid.

    I would add to that put the money that would have been wasted on redundant drives towards a quality SSD with ATA trim for a boot drive (move User folders, System Restore, Hibernate, and paging file to a mechanical drive; turn off readyboost, indexing, defragmentation, Write Caching, Superfetch for the SSD)

    SSD boot, more/faster RAM, and better/more Graphics cards will give better performance increases that Raid.

    Scheduled backups is a good alternative to Raid redundancy for the home use and NAS devices can be great for scheduling those backups
  • ardichokeardichoke Icrontian
    edited December 2009
    Pssh... I enjoy running a RAID in my home workstation. Then again, I actually understand how they work and have a separate, external, drive that I do backups to. That said, having a RAID 1+0 array is nice. Gives a marginal performance boost and I can lose 1 (or 2 depending on which 2) drives without having to reinstall and restore from backups. Most lusers however should stay the f*** away from RAID because they have no idea what they are doing.

    RAID != Backups
    RAID == SERIUS BUZINESS
  • lordbeanlordbean Ontario, Canada
    edited December 2009
    I likes me my RAID array as well, although I have lately begun to take data security into much larger account than I did previously. My setup at the moment is 4 drives in RAID5 with a hot spare.
  • ardichokeardichoke Icrontian
    edited December 2009
    Does your rig not support RAID6? Don't get me wrong, having a hot spare is nice... but if you're running RAID5 with a hot spare anyway you might as well have the extra parity already built and ready to go. Reduces the odds of having a 2nd failure while the array is rebuilding on the hot spare.
  • mertesnmertesn I am Bobby Miller Yukon, OK Icrontian
    edited December 2009
    ardichoke wrote:
    Does your rig not support RAID6? Don't get me wrong, having a hot spare is nice... but if you're running RAID5 with a hot spare anyway you might as well have the extra parity already built and ready to go. Reduces the odds of having a 2nd failure while the array is rebuilding on the hot spare.
    Most RAID controllers on motherboards don't support RAID6 - they stop at RAID5. You'll have to get an add-on board for RAID6.
  • photodudephotodude Salt Lake, Utah Member
    edited December 2009
    mertesn wrote:
    Most RAID controllers on motherboards don't support RAID6 - they stop at RAID5. You'll have to get an add-on board for RAID6.

    If your doing raid you should have an add-on board (as I recall ardichoke has an add-on board for his raid)
  • lordbeanlordbean Ontario, Canada
    edited December 2009
    It isn't strictly necessary with ICH RAID, although a controller would be more portable if I were to switch over to an AMD system. As I understand it, ICH RAID revisions are pretty much cross-compatible - ICH7 can read ICH10 RAID, and vice versa.
  • ardichokeardichoke Icrontian
    edited December 2009
    I actually don't have an add-on board for my desktop :-/ Then again, since I'm doing RAID1+0 instead of RAID5 I don't really see any performance hit from it.
  • mas0nmas0n howdy Icrontian
    edited December 2009
    Arrays that require parity is where the hardware controller really pays off, but being able to do cached read/writes is also awesome.
  • Ob-v8Ob-v8 SF Bay Area
    edited January 2010
    First off, I simply wanted to mirror my HDD, and have a real-time copy of C: and D: (traditional lettering scheme). I see RAID1 as an automated system for mirroring HDDs. I know what a true backup is, and I do use some DVDs in addition to the 4 drives (2 int. SATA for RAID1, 1 int.IDE for manual clones, 1 ext. and 1 off-site IDE for clone storage) where my files are going to reside when I get RAID to behave.

    Second, I don't think this should be rocket science, either hardware or software; if non-RAID HDD operations are robust to issues (from power to minor hardware failures), and don't require a degree in CS, then for Pete's sake so should RAIDed HDDs! Correct me if I'm wrong but aren't RAID1 controllers simply channel splitters, either in parallel or series? (WAG)

    Ah, nevermind that (blowing off steam), WTF is up with RAID metadata? Secret code, super-double secret area for storing the block... jeeminey christmas. Some people need to get over themselves and - JOIN THE TEAM. Standards people; put your shiz where everyone else does: in the boot sector! Where I could find it and delete it if need be had eh?

    I'm ticked-off about the metadata because of my experience with RAID1. I got a mobo w/onboard RAID. I thought it was hardware, but I am told the Silicon Image "SiI3114 SATARAID Controller" is but a 4-port SATA to PCL bridge... anyways, what I want to know is this: spinner says in his posts that one will not get an OS like XP to work from a software RAIDed HDD.

    Reason I want to know is I put my loaded OS disk into RAID1 (using the "copy data" command in the manual build routine) as the source disk, and now there is no bootable HDD. FWIW, Silicon Image's utility offers no data loss warning (I'm so used to those I thought clone to new HDD and voila!). The data is there; I can see it (read on).

    Now I salvaged my files by cloning the source to target myself (old Acronis bootable CD) so I could access them with a fresh install of XP on my int.IDE, but before I waste my time loading XP onto the now working RAID1 array I want to know if XP will work from within a software RAID1 array.

    Thanks for overlooking my pissin' and moanin', or being entertained by it.
  • kryystkryyst Ontario, Canada
    edited January 2010
    It will work if you can see the raid partition from the boot cd either directly because your mobo handles it correctly or through a secondary driver disk that can be loaded at the start of your windows installation (that Press F2 option right at the beginning).
  • photodudephotodude Salt Lake, Utah Member
    edited January 2010
    Ob-v8 wrote:
    First off, I simply wanted to mirror my HDD, and have a real-time copy of C: and D: (traditional lettering scheme). I see RAID1 as an automated system for mirroring HDDs.

    Correct me if I'm wrong but aren't RAID1 controllers simply channel splitters, either in parallel or series?

    WTF is up with RAID metadata? Where I could find it and delete it if need be had eh?

    I put my loaded OS disk into RAID1 (using the "copy data" command in the manual build routine) as the source disk, and now there is no bootable HDD.


    RAID1 does mirroring but not in the way your thinking. it's a 1:1 mirror It only mirrors a single drive within the array, every drive is the same in the array. Raid1 also has a performance hit due to the multiple simultaneous writes. note: mirroring is not cloning. if you get data corruption in raid 1 it will be on all drives in the array. Raid 1 is only for a mechanical failure safety net. and will always require two drives as a minimum.


    RAID1 controllers are not simply channel splitters, a channel splitter would take [data A] and split it into [data B] + [data C] which is also different then stripping that Raid 0 does.

    Raid doesn't work with the type of delete-able metadata that your thinking of any type of corruption to controller files can cause a systemic failure that will prevent reading of the data on the drives.

    Copying data from a boot drive to a RAID array via copy will not give you a boot drive, the same thing applies with copying data from Drive A to Drive B Drive B will not be boot-able. you have to use a program like ghost.
  • Ob-v8Ob-v8 SF Bay Area
    edited January 2010
    kryyst wrote:
    It will work if you can see the raid partition from the boot cd either directly because your mobo handles it correctly or through a secondary driver disk that can be loaded at the start of your windows installation (that Press F2 option right at the beginning).

    Thank you kryyst,

    so if I can load XP onto a RAID partition then I can boot XP from it. I'll give it a go.
  • Ob-v8Ob-v8 SF Bay Area
    edited January 2010
    photodude wrote:
    RAID1 does mirroring but not in the way your thinking. it's a 1:1 mirror It only mirrors a single drive within the array, every drive is the same in the array. Raid1 also has a performance hit due to the multiple simultaneous writes. note: mirroring is not cloning. if you get data corruption in raid 1 it will be on all drives in the array. Raid 1 is only for a mechanical failure safety net. and will always require two drives as a minimum.


    RAID1 controllers are not simply channel splitters, a channel splitter would take [data A] and split it into [data B] + [data C] which is also different then stripping that Raid 0 does.

    Raid doesn't work with the type of delete-able metadata that your thinking of any type of corruption to controller files can cause a systemic failure that will prevent reading of the data on the drives.

    Copying data from a boot drive to a RAID array via copy will not give you a boot drive, the same thing applies with copying data from Drive A to Drive B Drive B will not be boot-able. you have to use a program like ghost.

    I was thinking of mirroring a 1TB physical drive, divided into two 500GB logical drives (C: & D: ), onto another 1TB physical drive. I'd like to say I'll clone the mirror to ext.IDE monthly, but that relies on me... so maybe I should get Acronis True Image to schedule said external copies? Then quarterly the ext.IDE gets pulled to an offsite location (i.e. work) for "offsite storage".

    I'm not worried about performance - otherwise I'd be smokin' the RAID0 teat eh? I want fault tolerance; if a physical or logical drive goes down, I have a mirror ready and waiting.

    If RAID doesn't simply write data to two drives simultaneously then WTF is it doing? Why does crap have to be so complicated? Why is a mirror not a clone, specifically? (I really do like to learn.)

    RAID metadata should simply be an ID note to the controller, and a disk access lock, eh? Why does it have to be something that can cause data loss? No, really, that is an honest and reasonable question.

    Thanks for the reminder on the copying issues; I have been lost in RAIDland and I have pretty much forgotten everything else (cursed at my computer for a bit until I remembered I had to load the mobo drivers to use the LAN... :)
  • lordbeanlordbean Ontario, Canada
    edited January 2010
    Ob-v8 wrote:
    I was thinking of mirroring a 1TB physical drive, divided into two 500GB logical drives (C: & D: ), onto another 1TB physical drive. I'd like to say I'll clone the mirror to ext.IDE monthly, but that relies on me... so maybe I should get Acronis True Image to schedule said external copies? Then quarterly the ext.IDE gets pulled to an offsite location (i.e. work) for "offsite storage".

    Offsite storage is probably the best choice you can make in the event you need to do disaster recovery.
    I'm not worried about performance - otherwise I'd be smokin' the RAID0 teat eh? I want fault tolerance; if a physical or logical drive goes down, I have a mirror ready and waiting.

    This is essentially what RAID1 is for - a physical drive failure can be tolerated by the system as it can continue to run off the other hard drive. It does not, however, cover software disasters - keep reading for why.
    If RAID doesn't simply write data to two drives simultaneously then WTF is it doing? Why does crap have to be so complicated? Why is a mirror not a clone, specifically? (I really do like to learn.)

    A mirror RAID array does in fact simultaneously read and write to both drives, but the heads are always in the same position, which means that overall performance is actually slightly lower than a single drive - both disks must perform the random seek before reading and writing can occur. When writing, the same set of data must be written to both disks, and when reading, both sets of data must be read back in order to check the integrity of the data.

    In addition, a mirror does not provide you with disaster recovery in the event of a software issue because the same problems caused by the software are written to both drives in the array. For this reason, backing up your files is still important for recovery purposes.
    RAID metadata should simply be an ID note to the controller, and a disk access lock, eh? Why does it have to be something that can cause data loss? No, really, that is an honest and reasonable question.

    I'll pass this one to someone else who knows more about the tech...
    Thanks for the reminder on the copying issues; I have been lost in RAIDland and I have pretty much forgotten everything else (cursed at my computer for a bit until I remembered I had to load the mobo drivers to use the LAN... :)

    It actually is possible to copy an operating system from one drive to another, but there are some rules to follow and some hoops to jump through to do it successfully. Unless you have a very good knowledge of the NT5 & 6 command prompts and the tools provided therein, it's not a good idea to attempt an OS move without using a third party tool.
  • edited August 2011
    kryyst wrote:
    I just need to say this - take it for what you will.

    Stop putting raids in your home systems unless you understand how they work, understand the risk/rewards of using them and more importantly understand how to recover them when they fail. Oh and they will fail, every raid fails.

    Also if you really want to run raid, make sure you are backing up whatever is on the raid. Then when the raid fails (and it will fail) you can kill the raid, rebuild it and recover from your backup. Without having to mess around trying to rebuild a raid.

    One more thing. If you are running a raid (again home systems) make sure you are running a seperate raid controller and doing hardware raid also. Onboard raid controllers suck for 2 reasons. One if the controller fails you can replace the controller not the whole motherboard and secondly they are typically more reliable and come with better tools to repair your raid - when it fails. If you are running software raid, well god help you.

    Raid types. If you feel the need to run raid don't run raid 0. Simple as that. If you want reliability run Raid 1, if a drive fails basically no biggy. But know that raid 1 is primarily for redundancy and not speed. Raid 5, rather popular put in 3 (or more) drives loose 25% of your space and gain almost no benefit on a home computer because guess what - you are the only person using it so the data access is rather singular. You don't have a whole tone of multiple read/writes in the cue.

    Pleas people I know I'm ranting but it's a lesson that many need to learn. Raids are ideal in the business world where you have high volume, highly accessed data stores they are also running on server class machines that are designed to do it.

    Raid on your home computer not worth it.

    Rant off.
    Thank you - someone finally said it!!!:tongue:
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