Hi, ive just bought my second Seagate Barracuda 7200.7 and I want to create a RAID 0 array. The only thing that im confused about is stripe size, my mobo manual says to go for smaller stripe sizes for servers and higher ones for multimedia machines. But im still unsure as to exactly which size to choose. Ill be using the machine for pretty much gaming only. Sometimes a bit of music. What size should I use?
you shoudn't, because you shouldn't use RAID0 it presents no real performance advantage in a single-user environment and adds additional risk of losing data There are very few reasons to use RAID0, and gaming certainly isn't one of them
I was told I would notice a performance increase if I went with RAID 0. I would only lose data if one of the disks failed wouldnt I? So wouldnt that mean theres not that much more risk when compared to a single HDD as that could also fail and cause you to lose data. Ah well, so if RAID really is a bad idea for a single user rig what shoudl I do?
In transfer speed IS a noticable increase. If you transfer lots of files from/to sources that are faster than a single disk it is noticable. Sequential reads are just lots faster with RAID0. If you keep your drives defragmented, you should even be able to notice some difference when loading games. (defragmented so data will be sequential, thus you get faster readspeed) The downside is that your data is more vulnerable to crashing disks. If you have two seperate disks, and one crashes, the other one holds its data. In RAID0 all data that was on both drives will be unreadable, even if one drive does not crash but the other does. I don't think RAID is such a bad idea, but only if your data is not important. If you have important data on your RAIDed disks, there is just too much danger of losing the data imho. edit: By the way, what about RAID1 (mirror RAID)? Again you use two disks combined, but this time they are exact copies of eachother (keeping data safe when one disk crashes). Should read speed increase with such a setup, at the cost of write speed?
Try 64k as a "general" size. (I'm not "up" on raid in the slightest btw, however rather than tell you you're a bit of a silly fool using raid0 I'm trying to actually answer the question you asked.... Guys he didnt say "shall I raid0 by drives, nor did he say "Is raid0 a good idea" he simply asked what the best stripe size was. There are many people with more knowledge on this subject that me about, can someone answer his question.... )
Well ive thought about it and TBH my data isnt that valuable. I mean sure it will be annoying to have to reinstall everything and I may lose a few un-recoverable bits of data but its nothing that cant be backed up on a single CD every once in a while. The rest like music and games can easily be restored, it just might take some time. Looks like ill be going for it then, even if it does put my data at risk. Im guessing I should go for a 64k stripe size then?
you may notice a second here or a second there in game loading times (i say "notice" but I've got a feeling you may not unless you're really looking for it), but those seconds will be added on elsewhere if youre throwing your OS on to the array. To put it into perspective, on my RAID5 setup (massively faster than a couple of 7200.7s in RAID0, and on a top-end 500 quid controller, ie no real overheads for parity calculations) game loads are around 2x the speed as running them on a single drive If you're determined to use RAID0 (Though I think you may realise just how important you think your data really is in the event of a disk crash) give 64k a go, that should fetch you towards the high end of the transfers (but your OS won't like it much)
Hm, youve kinda knocked me back with that one. How much slower do you reckon the OS will be? And will it be slower just when booting or when performing simple tasks aswell?
RAID0 is good at dealing with large files very quickly, which is why game loading times can benefit slightly from using RAID0 (the same can be said for content creation, but RAID0 should only really be used if you cant afford RAID10 in those cases). Often a game can read several hundred MB of files into memory. Windows, and most applications youre likely to be using, are made up of thousands of small files. The result of this is that you have lots of random access patterns, and have a lot more writes (not truly random, but a long way from the sequential reads you have in games), RAID0 isnt going to be helping out here. Another thing to consider is that onboard controllers arent great, and the only time they should be used IMO is RAID1 (RAID1 has just about zero overhead, and it tends to be the case that the disks are accessible outside the array, ie just 2 drives with identical contents). If the board dies, or just the onboard controller, your array is also hosed.
I see. Well those one or two seconds gained in loading time will add up for me as I spend alot of my time gaming, both with FPS and large scale MMO's. So I would be able to put up with a minor hit to OS performance if it means shorter loading times. But just how great is the hit to the OS? And with RAID1 it would be sort of pointless for me as hardly any of my data is valuable and rates are slightly slower than a single drive. I also lose half the capacity.
you seem pretty determined, but I can say with 99% certainty that you will not get massive gains from using RAID0. You do realise that even if you are gaming in solid 24 hour sessions, you may save a minute at the end of it all. Unlike in games, where striping will give you a second or so every time a loading screen pops up (but do nothing to framerates), RAID0 will take a bit more time to do pretty much every little action when youre in windows, every time you make a disk access basically. Youre talking fractions of a second here, but with the way youre analyzing this it will add up to more at the end of the day. I wasn't saying you should use RAID1, I was just saying that thats the thing onboard controllers can do well as there is very little calculation involved and no risk from using on onboard solution. IMO RAID1 isnt ever a feasible solution because of the storage efficiency (or lack thereof) If you must use RAID0, consider having 3 drives with your OS and applications on a single drive and your games and storage on the array. With the price of storage these days, an additional drive isnt going to break the bank. Its up to you mate, you've got the facts before you, do with them what you like. (though I do think you may be underestimating the amount of hassle caused by losing everything)
Thats a very good idea. I hadnt thought of using three drives, would certainly give me the minor advantages of RAID0 without the higher risk of losing data and slower OS operation. I had already begun setting up the array (im typing this on my laptop) before I stopped to think, initially about stripe size but then I got into why I actually needed RAID0 and what the drawbacks were so my drives have already been wiped so I think ill just set up the array and order another drive to add later on. Of course it will mean wiping again once the new drive arrives as the OS will have to moved to the new disk but that doesnt really bother me. Cheers for all the advice, really has helped.
I totally agree with this. People always comment about the unreliability of RAID0, but it's going to be exactly the same risk as a single hard drive of the same size of the array.
wrong. the collective MTBF of a 2 disk RAID0 array will be exactly half that of a single drive, 1/4 for a 4 disk array 1/6 for a 6 disk array etc This means that on a 2 disk RAID0 setup, you're doubling your chances of losing everything from a drive failure over a single drive Under your principle, running a several hundred drive RAID0 setup isn't any less reliable than a single drive. The actual fact of the matter is that the data on the array would be lucky to last a week
So you say if 2 identical drives do exactly half the work, they will live half as long... Logic doesn't support that... [rant] But Mister_Tad, like I've said before, I love your degree of expertise, but I hate it every time someone mentions raid0 you jump on it telling that it isn't worth it, over and over again (3 times in this thread alone), while it even wasn't the question in the OP.[/rant]
that's not at all what I'm saying (and they will still be doing the same amount of work as running standalone) you're misunderstanding what MTBF means, it doesnt mean "this drive will last this long". It works more along these lines: A drive with a 1m hour MTBF means that if you run 1m of those drives concurrently, youre likely to lose one drive every hour people tend to greatly misunderstand exactly what RAID is and how it works RAID0 is a worse idea than a lot of people realise As a comparison (there are numerous i could use, this is just one), there have been posts in the cooling forum along the lines of "how can I build a contained LN2 system" It is indeed possible, and the thread could have gone into an in depth discussion as to exactly how its done, but its just not a good idea. Now a post saying "you dont, its not feasible and it probably wont work" isnt explicitly answering the original question, but it is none the less helping out the member asking the question. The original question of the OP has been answered, and he has gone on asking additional questions about the ups and downs of RAID0, which I have been asnwering. I've just been giving the facts Even Hamish, who is a proper RAID0 fanboy (sorry dude, you know you are though ) has advised against it in his case
I can't really see that much wrong with that. If someone thinks that a member has got the wrong idea or is doing something that isn't really worth it, it's more than reasonable to say so; it might not answer the original question, but it's giving useful advice. If someone asked "Hey, what is the best sealant to use when i water cool my case so it doesn't leak out when i fill it?", you wouldn't get "Oh, I'd recommend this stuff, does a great job". You'd get "For the love of God man, don't do it!". It might not answer the original question, but it does still constitute something quite useful
Well, saying doesn't bother me. I find it good that you note it, but when you keep repeating it, it does bug me. We aren't children in here, if you get warned, you consider it, and decide if you do it or not. But like I said, I think it's a good thing that you share your expertise. Mean Time Between Failure right? What you tell is true for huge amounts of disks. But it's oversimplification just to say it's true for 2. Statistics don't work that way. Odds are that they will last shorter, but the odd are the same that they'll last as long, or maybe longer then standalone disks. If you are unlucky, you get a drive which fails soon, and the array is lost, but if you are lucky you get 2 drives which go on for ever, and nothing ever happens. Just pure luck. Doesn't RAID0 means that 1/2 of the data is written on both drives? Then they roughly do half the work, don't they? What else are they doing? Raiding disks doesn't change the physical process of writing/reading from the disks. The drives read and write in exactly the same way. There for there shouldn't be any reason why they fail earlier. But maybe we have a different definition of a hard drive failure. For me it is 100% physical, the drive stops working. Maybe for you it is the data is lost. Data loss is a different thing, because of the array, there is a higher chance of bad writes, I totally agree on that, but that's due to the controller (which can make mistakes/errors), and the more complex process, not due to the (physical)drives.
They do half the writing each, but the actual movement is around the same as it would be normally. Imagine you want to write one file of, say, 256KB in size. In a normal single-disk configuration, the drive will (ideally) find a block of empty space and position the head once above it and write the file with no movement. That gives one total actuator movement. In your RAID 0 array, the file is broken into four stripes and two are sent to each disk. This means that both drives have two stripes to write, so both will position the heads above a free, contiguous space and write to disk. This gives one actuator movement per drive for this write as well. Of course, this is in an ideal scenario; if there aren't any contiguous stripes, there will be more actuator movement than normal because it has to find a free section and write them there - this is particularly applicable for large files. Same thing occurs with fragmentation, but this will affect the single drive also. Of course they aren't totally applicable - however, logic would dictate that if you have one drive with a particular reliability rate, doubling the number of drives would double the possibility of failure. RAID 0 is less reliable for exactly this reason.
