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Question about RAID...


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#1
erndawg101

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So I've got a new system and I'm thinking about purchasing a RAID PCI controller card to hook up the hard drives too. My question is how does this work exactly? Do I have to configure anything for the mirroring to take place? Do the hard drives have to be RAID compatible or will any SATA hard drive work? If i hook up four drives to two different cards will 1 be mirrored to 2 and 3 mirrored to 4? 1 & 2 would be on the first card and 3 & 4 would be on the second card. I can post system specs if the information will help. Thanks in advance for your answers.
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#2
SRX660

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Please read this on raid.

http://www.ahinc.com/raid.htm

A thought here is to check your motherboard spec's to see if you already have a raid setup for the SATA drives. Many MB's do have the raid for SATA drives built into the bios.

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#3
Kemasa

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The first response is a question, what data are your protecting and why do you think you want to use a RAID setup? I personally think that RAID devices are great, but often people don't need them as they are protecting only a small amount of data which can be better backed up through other means. RAID is not 100% and does not mean you don't need to make a backup.

It might be that a couple of external drives and backing up the data every day will provide more protections than using RAID.

You will have to configure the setup and there are choices, such as RAID0 (not suggested unless you need a large data space and need no protection), RAID1, or RAID5 (there is also RAID3 too, but not as common in the PC world).

The drives don't have to be certified for RAID or anything, most drives will work, but all the drives should be the same. Also, you need to consider how you attach the drives. For example, using EIDE drives you don't want to use the slave device since if the master has a problem, the slave will not be accessible and you could lose data.

One thing that people don't think about with RAID is that you are trading space for redundancy. In the case of RAID1, two disks of 200Gb will become one RAID volume of 200G. In the case of RAID5, the space available will be one disk less than the number of disks, so if you have 4 disks of 200Gb, you will only have 600Gb of usable space. There is also an overhead associated with RAID. In the case of RAID1, both disks have to have the data written to them. In larger systems this is not as much of a problem, but in PCs this can mean that the speed is reduced.
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#4
warriorscot

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See im the opposite RAID is way over rated for me it has one environment where its worthwhile and thats the one it wsa made for, corporate servers and large scale data storage systems. In the home environment they are difficult and only serve to increase overheads and reduce performance which isnt neccesary as a home pc unlike a corporate server is manned all the time and doesnt need the automation. Backing up files is easily and quickly done without RAID the setting up of raid can be difficult and there is maintanence you dont have to rebuild a collapsed DVD but a raid array is a pain to put back together.

Personally i always think its easier to keep your files that are important backed up on another partition or internal drives(external i just dont get the logic unless you have no internal space left). And optical is a much safer backup medium for your important data as hard drives like all mechanical devices have an operational lifetime and they are particularly sensitive to external factors.

The way i protect my important files is to back my large files to disk as soon as possible and i keep them on my data partition. The smaller files i use more regularly like pdfs, documents etc. get saved to my USB pen whenever i make any changes and i can carry that safely around and have backups(i also back this up to DVD ram everynow and then).

You have to balance wether you need the hassle of raid and the sacrifce of disk space. Also keep in mind that DVDs are incredibly cheap the costs are a like a fith of a penny per Gb Hard drives can run as much as 30p or more per gb.

Edited by warriorscot, 01 May 2006 - 06:48 PM.

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#5
Kemasa

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A home PC is not manned all the time, often people leave the computer on. Also, home PCs are used for many things, so rather than trying to classify machines as to where they are located, you need to look at what the machine is being used for.

You are correct that often is is easy to backup files that change, but then you have to decide how much data you are willing to lose (the time between backups). If you don't want to lose any data, then you end up with RAID1 as you constantly backup the data. On some systems you can could setup a RAID partition using only part of the disk, which could then be used for user data and not the operating system. This would not help those who use their home machine for critical use though.

Also, I have heard some reports that optical media is not as good as some people think that it is. The good part is that it is fairly cheap and you make make multiple copies. As far as cost, I have seen disks cheaper with some of the deals and rebates, but honestly each has its own good points and bad points and so each can not replace the other.

If you want to do the best thing, you would have a RAID volume and often do backups. I do agree that the effort is not worth it for most people to deal with RAID volumes. It is also true that many people don't do backups, which RAID helps with, but does not replace.
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#6
JourneyMan

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I think a RAID0 with a bunch of small, cheap SATA hard drives is the way to go. You add up the HD space in RAID0, so you'll get good capacity easily. Keep backups on a seperate bootable hard drive and everthing is good to go.

Personally, I'm going to RAID up 3 80gig SATA HDs and put WinXP64 on it when I can get some extra money saved up and just use the HD I have right now as my 'work' drive.

My games will be faster and I'll be able to concentrate easier on my work :whistling:

Edited by JourneyMan, 01 May 2006 - 10:37 PM.

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#7
Rockster2U

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I have to go with guy in the middle of the fog up on the hill by the lake. For the average person, RAID mirroring is wasted drive space and striping produces a very minimal performance gain while creating a somewhat risky configuration. (it ain't what its cracked up to be) A commercial environment is all together different and I'd call mirroring almost mandatory for most businesses. Having said that, the home user is probably going to be better served by making images of their system on a fairly regular basis and using a tool like Replicator to make automatic daily data backups to a second drive. From a practical standpoint, if a drive goes south, one can rebuild a system from a fairly current image and a good set of backups faster than rebuilding the mirror. Sure, if you have a mirror and one drive is lost, there is no downtime but if you want to rebuild your system, you still have to rebuild the mirror.

:whistling:
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#8
Kemasa

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One thing to keep in mind is that it is not about what we each personally think, but what is best for the person who is going to use the system, which has to be based on what they are doing, how critical their data is and how much data they are willing to risk losing. If you don't ask what the person is using the computer for, what data they have, how critical is it, you really should not be making blanket recommendations since every situations is different.

I am not sure of why it is claimed that mirroring is a risky configuration, nor why it would be almost mandatory for most businesses. Perhaps in a small environment RAID1 would be good, but anyplace with much data can not afford the data loss and so RAID5 is a much better choice. If you look at large data installations you will typically not see RAID1.

RAID0 is an interesting concept since there is no "R" in it. Lose one disk and you lost everything. RAID0 is a good if you need a large data space and don't care about the data being lost, but otherwise it is not a good idea and I would not consider it a good suggestion to others unless they understand what they are getting themselves into, plus on a PC platform I doubt that you will see much of a speed improvement and could see reduced speeds, especially if you don't have a hardware RAID controller.
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#9
Rockster2U

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Kemasa, you are taking some editorial liberties. No one said mirroring is a risky configuration. A careful re-read will net the following

..... and striping produces a very minimal performance gain while creating a somewhat risky configuration

I'll stand by that comment and I'll also stand by the comment that A commercial environment is all together different and I'd call mirroring almost mandatory for most businesses. You are very correct that RAID 5 is a safer and more practical solution for organizations handling very large volumes of data.

:whistling:

Edited by Rockster2U, 02 May 2006 - 03:55 AM.

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#10
warriorscot

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Lol, well given that the user hasnt come back to give us specifcs you can only give your general opinions making sure that you qualify your statements as we all have. Raid is something ive never seen any large organisation operate without or if not RAID the standard backup system of tapes. Also a "home" machine isnt a classifcation of where it is its a classification of how it is used as well, and since people coming here are supposed to be non corporate most are going to be talking about a home use PC or one used in a similar way.

Also Journeyman buying seperate 80Gb usually costs more than getting a large single drive and its difficult to get a 16mb cache 80 and a single 16mb cache large drive would outperform a Raid of 8mb cache 80s. You would also get alot more storage in a single drive for your money generally as a rule.
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#11
erndawg101

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Windows: Windows XP5.1 (Build 2600) Service Pack 2
Internet Explorer: 6.0.2900.2180
Memory (RAM): 2048 MB
CPU Info: Intel® Pentium® D CPU 3.40GHz
CPU Speed: 3390.5 MHz
Sound card: Realtek AC97 Audio
Display Adapters: NVIDIA GeForce 6600 GT | NetMeeting driver | RDPDD Chained DD |
Screen Resolution: 1280 X 1024
Network: Network Present
Network Adapters: Realtek RTL8169/8110 Family Gigabit Ethernet NIC - Packet Scheduler Miniport |
CD / DVD Drives: D: HL-DT-STDVDRAM GSA-H10A |
Default Printer: Lexmark 8300 Series
COM Ports: COM1 | COM2 |
LPT Ports: LPT1 |
Mouse: 5 Button Wheel Mouse Present
Hard Disks: C: 232.9GB |
Hard Disks - Free: C: 91.9GB |
USB Controllers: Detected: 5 host controllers.
Firewire (1394): Not Detected
PCMCIA (Laptops): Not Installed
Manufacturer: American Megatrends Inc.
Product Make: MS-7176
Serial Number: To Be Filled By O.E.M.
AC Power Status: OnLine
BIOS Info: AT/AT COMPATIBLE | 12/12/05 | A M I - 12000512 | |
Time Zone: Eastern Standard Time
Battery: No Battery
Motherboard: MSI MS-7176
Modems: Not detected


Basically what it boils down to guys is I have the space for 4 SATA 250GB HDD's and Raid is onboard, so I can work with 500GB of space and have the whole thing mirrored, and afford to do it financially, so I've almost got a "why not?" point of view on it. But let me know what you all think. I'm enjoying reading the different points of view. This IS a home use PC by the way.
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#12
warriorscot

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Well then personally i would probably rather have the almost a terabyte of space to play with rather than a Raid, if you want to you can certainly try it if you need more space you can just break up the array and use the other disks normally. Performance wise you wont gain anything from it though and if its just a home system you are as quick just copying older files over onto the other drive. What i would maybe do if you want to try raid is have two drives in raid and then have the other two as normal drives then you have a backup of one of the drives you can use for essential data.

But with 4 drives you can always play around with it if you like, you could try some different raids for a while see what you like but i would rather have the 4 disks and all that space. If its not about the storage or backup and just about the project of doing it then you may as well

Like i said with mirroring you can always break it up and just reformat that backup drives and get your space back. You have alot of options and if you have the money to buy the drives then you can do that quite safely, mind you on a home system its rare to need almost a terabyte of hard drive space ive only got 200 and even though i use alot of HD space myself i just burn my stuff to dvd after a little while and delete it off the drive.
I could buy a new drive but the new drive costs the same as well over a terabyte worth of DVDs and i can carry my dvds around and give them to friends etc and switch pcs easier. Optical is my prefered method of backup and ive always found it to be safer than HDD as they are less volatile and much easier to use.
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#13
Kemasa

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Kemasa, you are taking some editorial liberties. No one said mirroring is a risky configuration. A careful re-read will net the following
I'll stand by that comment and I'll also stand by the comment that A commercial environment is all together different and I'd call mirroring almost mandatory for most businesses. You are very correct that RAID 5 is a safer and more practical solution for organizations handling very large volumes of data.

:whistling:


Sorry, you are correct in that I mis-read your message where you mentioned mirroring and then striping.

I disagree about mirroring, most companies I have seen don't use that. Often there is a server with a RAID5 array, shared for network storage. The overhead with RAID1 is just too high for a business since generally most businesses have a fair bit of data, even if it is not a large amount overall.
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#14
Kemasa

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...
Basically what it boils down to guys is I have the space for 4 SATA 250GB HDD's and Raid is onboard, so I can work with 500GB of space and have the whole thing mirrored, and afford to do it financially, so I've almost got a "why not?" point of view on it. But let me know what you all think. I'm enjoying reading the different points of view. This IS a home use PC by the way.


If you have the money and interest, then I have to agree with you, why not do it? It will protect your data and you can learn about it. It does not mean that you don't need to do backups since RAID is not 100% perfect and you could lose your data.

To me the question is not whether it is a "home" PC, but what you do with it, what data you have on it and what degree of data loss you are willing to accept.

If the on-board RAID controller can do RAID5, you might consider that since it will get you more space. Otherwise you might create two RAID1 volumes.
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