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Pastimes : Dream Machine ( Build your own PC ) -- Ignore unavailable to you. Want to Upgrade?

To: Street Walker who wrote (434)	4/3/1998 10:42:00 AM
From: Spots	Respond to of 14778

>>Hardrives...stringging...mirroring....HELP I'm not familiar with the specific term "stringing" but it sounds like reference to NT's ability to make two (or more) physical drives appear as one large logical drive. ("String" them together.) This isn't a good idea; if one drive fails, NT will probably have a problem retrieving data on the others. Mirroring is writing two identical partitions on different physical disks. If one disk fails, the data can be accessed from the other, and the failed disk can be replaced to restore the mirror. This is the simplest full fault tolerance for disk data. Done right, it can also perform better than a single, unmirrored disk. Naturally, NT doesn't do it just right, so it costs you a bit in performance (or so I read). I run mirrored disks on a server where I keep my critical data. NOTE, though, that NT workstation will not support mirrored disks; it requires NT server. Also NT makes it hard for you to recover the mirrored data if the system partition is mirrored. There's no reason for this except general unfriendliness, but I'd avoid mirroring the system partition. Trouble is, disk failures often take a critical system component with them. Be sure you understand boot sector backups and have the disk tools and boot backups on floppies for emergency repairs, or all you're saved data is at risk after a failure. This is ESPECIALLY true if you mirror the system partition. Mirroring is a form of RAID; NT Server can also do higher-level RAID. Also, some disk controllers can do RAID (including mirroring), both IDE and SCSI. I have no experience with controller-based RAID. NT server mirroring saved a disk full of data for me once. Your rough table is more or less correct, with the caveat that these are theoretical maximum. Your actual mileage will vary (vary way below these). I've never been able to talk myself into the extra expense of SCSI over EIDE. I'd rather have 8 gigs of mirrored IDE for my 600 bucks. SCSI's potentially faster, but the later EIDE drives are F.A.S.T. too. Used to be IDE took a significant CPU resource, but that's old news too for today's screaming processors. However, many knowledgeable people swear by the overriding advantages of SCSI. I can't speak to that.

To: Street Walker who wrote (434)	4/3/1998 11:05:00 AM
From: LTBH	Read Replies (3) \| Respond to of 14778

Hard Drives, Striping and Mirroring plus Cases First, I attempt to not recommend single products. You are the purchaser. You are the one who will foot the bill and must be satisfied with the results. You are also the one who is supposed to be most informed on your circumstances and requirements. Instead I attempt to point out alternatives or correct misunderstandings and oversights in thinking. Along these lines, let me apologize in advance if some of my comments seem harsh. They are not meant to be unkind, but rather are intended to get you thinking on the correct plane. The best starting place is always the beginning. I have followed several of your posts and it is unclear to me whether you have established and researched the basic premises of your system. What exactly is your budget? What is the system's primary use? Will the system be used for other tasks? How much of your budget will be for HW and how much for SW? The one thing you appear sure of is that you will be running some kind of trading program. What are the resource requirements of this program? After determining your budget, this is the next thing you must research thoroughly. You are foolish attempting to select system components without a complete understanding of these requirements. I also have no knowledge of this type of application. For instance: what is the preferred OS for this app? Does it usually require use of multiple Virtual Machines (VM)? How much memory is required by the app? How much HD space? I infer that you are getting some kind of stock data as input to your app. How is this input? Is it via a modem link? If so, does a very slow modem link require expensive SCSI HDs and even more expensive SCSI RAID? Or are you using and can afford a dedicated high speed link? In this process you also need to check out various manufacturer and HW sites for yourself. They contain some excellent material and your informed decisions are much better than acting solely on someone else's opinions. It would take too much space to echo this material in a post. However, once you have communicated the basic parameters of your requirements, I would be happy to post some links that might assist informing you on specific areas. I will hold off on replying on the specifics of your two posts until we have a better understanding of the above. Networm

To: Street Walker who wrote (434)	4/3/1998 11:32:00 PM
From: Zeuspaul	Read Replies (1) \| Respond to of 14778

RAID....Striping.....mirroring.....harddrive cache For the trading machine I don't think RAID will make a difference. One way to tell is to watch the harddrive light on the computer. If it lights up you are writing to the harddrive. If the light lights up for a very short time you have written a small file. Small files will go to cache first and it will happen very quickly. If the file fits in cache SCSI and RAID will not increase performance. IBM drives have 512k cache. With 128MB RAM I do not think you will be writing any quotes to the harddrive nor the harddrive cache. If you do, increase the RAM. When you call up Tradestation you will see the harddrive light go on for a longer period of time as the program is recalled from storage. With a faster harddrive (SCSI or SCSI RAID) the program will call up more quickly (big deal). Also if you execute a save the save will be faster with a faster harddrive. When should you consider SCSI? SCSI should be considered as a system. If you want to add peripherals such as scanners, CD ROM, CDR, CD RW, multiple harddrives, ZIP or LS120, MO drives... go for SCSI. ALSO, you will have better luck with CD recording drives if they are in a SCSI based system. These drives require instant access to the files that they are recording. When should you consider SCSI RAID? (Network servers of course) Home movie editing requires fast harddrives. You need to pass very large files on a continuous basis. A standard IDE drive or most SCSI drives will not be able to keep up. If you work with large files ( 10 MB to 100MB +) and you don't like to wait for long saves. (I wait in excess of 5 minutes for some of my larger files to save) What is RAID? RAID level 0 is STRIPING. Striping divides a file and writes half (if you have two discs in the array) to one disc and half to the other disc. This happens at the same time so it happens about twice as fast. (the Promise IDE RAID does not appear to have this type of performance increase. My first reaction is to go for a 7500 or 10000 RPM SCSI drive in lieu of the Promise technology if you only want a marginal increase in performance) If you have four discs in the array the performance increase would be four times faster. RAID Level 1 is mirroring. Mirroring writes the same file to each of two harddrives. This is a file back-up system. If one harddrive fails you still have a copy of the same file on the other disc. RAID level 0/1 does both. There are more RAID levels but this is the basic concept. Comments It is hard to justify the cost. Adaptec has affordable controllers starting around $500. They do not work with Win95. Strange as that is where the multimedia applications are. Maybe that is why they are having trouble with their stock price:( excerpt form the Digidata site digidata.com >>The performance of electronic devices such as microprocessors has grown at a rapid pace, yet the electromechanical design of computer disks has limited their performance growth. Indeed, microprocessor performance has been doubling about every two years, while disk performance has taken ten years to double. A RAID controller overcomes this limitation by using parallel data paths to read and write information to the disks in a RAID array. Thus, it performs the operations of reading and writing information to several disks simultaneously. With four data disks, for example, a RAID system can read and write information at a rate almost four times the rate of a single disk. Such high performance enables demanding applications, such as real-time video editing, to be accomplished that would otherwise be impossible or extraordinarily expensive. RAID controllers can organize data on the disks in several ways to offer performance advantages for different types of applications; the chart below classifies the most common methods.<<