硬盘的RAID0.1.5等等用途是什么，硬件和软件都如何组建！_百度知道
硬盘的RAID0.1.5等等用途是什么，硬件和软件都如何组建！
谢谢大家的帮助！
提问者采纳
RAIDCPU performance has been increasing exponentially over the past decade, roughly doubling every 18 months. Not so with disk performance. In the 1970s, average seek times on minicomputer disks were 50 to 100 msec. Now seek times are slightly under 10 msec. In most technical industries (say, automobiles or aviation), a factor of 5 to 10 performance improvement in two decades would be major news, but in the computer industry it is an embarrassment. Thus the gap between CPU performance and disk performance has become much larger over time.As we have seen, parallel processing is being used more and more to speed up CPU performance. It has occurred to various people over the years that parallelI/O might be a good idea too. In their 1988 paper, Patterson et al. suggested six specific disk organizations that could be used to improve disk performance, reliability, or both (Patterson et al., 1988). These ideas were quickly adopted by industry and have led to a new class of I/O device called a RAID. Patterson et al. defined RAID as Redundant Array of Inexpensive Disks, but industry redefined the I to be “Independent” rather than “Inexpensive” (maybe so they could use expensive disks?). Since a villain was also needed (as in RISC versus CISC, also due to Patterson), the bad guy here was the SLED (Single Large Expensive Disk).The basic idea behind a RAID is to install a box full of disks next to the computer, typically a large server, replace the disk controller card with a RAID controller, copy the data over to the RAID, and then continue normal operation. In other words, a RAID should look like a SLED to the operating system but have better performance and better reliability. Since SCSI disks have good performance, low price, and the ability to have up to 7 drives on a single controller (15 for wide SCSI), it is natural that most RAIDs consist of a RAID SCSI controller plus a box of SCSI disks that appear to the operating system as a single large disk. In this way, no software changes are required to use the RAID, a big selling point for many system administrators.In addition to appearing like a single disk to the software, all RAIDs have the property that the data are distributed over the drives, to allow parallel operation. Several different schemes for doing this were defined by Patterson et al., and they are now known as RAID level 0 through RAID level 5. In addition, there are a few other minor levels that we will not discuss. The term “level” is something of a misnomer since there is n there are simply six different organizations possible.RAID level 0 is illustrated in Fig. 5-19(a). It consists of viewing the virtual single disk simulated by the RAID as being divided up into strips of k sectors each, with sectors 0 to k – 1 being strip 0, sectors k to 2k – 1 as strip 1, and so on. For k = 1, ea for k = 2 a strip is two sectors, etc. The RAID level 0 organization writes consecutive strips over the drives in round-robin fashion, as depicted in Fig. 5-19(a) for a RAID with four disk drives. Distributing data over multiple drives like this is called striping. For example, if the software issues a command to read a data block consisting of four consecutive strips starting at a strip boundary, the RAID controller will break this command up into four separate commands, one for each of the four disks, and have them operate in parallel. Thus we have parallel I/O without the software knowing about it.RAID level 0 works best with large requests, the bigger the better. If a request is larger than the number of drives times the strip size, some drives will get multiple requests, so that when they finish the first request they start the second one. It is up to the controller to split the request up and feed the proper commands to the proper disks in the right sequence and then assemble the results in memory correctly. Performance is excellent and the implementation is straightforward.RAID level 0 works worst with operating systems that habitually ask for data one sector at a time. The results will be correct, but there is no parallelism and hence no performance gain. Another disadvantage of this organization is that the reliability is potentially worse than having a SLED. If a RAID consists of four disks, each with a mean time to failure of 20,000 hours, about once every 5000 hours a drive will fail and all the data will be completely lost. A SLED with a mean time to failure of 20,000 hours would be four times more reliable. Because no redundancy is present in this design, it is not really a true RAID.The next option, RAID level 1, shown in Fig. 5-19(b), is a true RAID. It duplicates all the disks, so there are four primary disks and four backup disks. On a write, every strip is written twice. On a read, either copy can be used, distributing the load over more drives. Consequently, write performance is no better than for a single drive, but read performance can be up to twice as good. Fault tolerance is excellent: if a drive crashes, the copy is simply used instead. Recovery consists of simply installing a new drive and copying the entire backup drive to it.Unlike levels 0 and 1, which work with strips of sectors, RAID level 2 works on a word basis, possibly even a byte basis. Imagine splitting each byte of the single virtual disk into a pair of 4-bit nibbles, then adding a Hamming code to each one to form a 7-bit word, of which bits 1, 2, and 4 were parity bits. Further imagine that the seven drives of Fig. 5-19(c) were synchronized in terms of arm position and rotational position. Then it would be possible to write the 7-bit Hamming coded word over the seven drives, one bit per drive.The Thinking Machines’ CM-2 computer used this scheme, taking 32-bit data words and adding 6 parity bits to form a 38-bit Hamming word, plus an extra bit for word parity, and spread each word over 39 disk drives. The total throughput was immense, because in one sector time it could write 32 sectors worth of data. Also, losing one drive did not cause problems, because loss of a drive amounted to losing 1 bit in each 39-bit word read, something the Hamming code could handle on the fly.On the down side, this scheme requires all the drives to be rotationally synchronized, and it only makes sense with a substantial number of drives (even with 32 data drives and 6 parity drives, the overhead is 19 percent). It also asks a lot of the controller, since it must do a Hamming checksum every bit time.RAID level 3 is a simplified version of RAID level 2. It is illustrated in Fig. 5-19(d). Here a single parity bit is computed for each data word and written to a parity drive. As in RAID level 2, the drives must be exactly synchronized, since individual data words are spread over multiple drives.At first thought, it might appear that a single parity bit gives only error detection, not error correction. For the case of random undetected errors, this observation is true. However, for the case of a drive crashing, it provides full 1-bit error correction since the position of the bad bit is known. If a drive crashes, the controller just pretends that all its bits are 0s. If a word has a parity error, the bit from the dead drive must have been a 1, so it is corrected. Although both RAID levels 2 and 3 offer very high data rates, the number of separate I/O requests per second they can handle is no better than for a single drive.Figure 5-19. RAID levels 0 through 5. Backup and parity drives are shown shaded.RAID levels 4 and 5 work with strips again, not individual words with parity, and do not require synchronized drives. RAID level 4 [see Fig. 5-19(e)] is like RAID level 0, with a strip-for-strip parity written onto an extra drive. For example, if each strip is k bytes long, all the strips are EXCLUSIVE ORed together, resulting in a parity strip k bytes long. If a drive crashes, the lost bytes can be recomputed from the parity drive.This design protects against the loss of a drive but performs poorly for small updates. If one sector is changed, it is necessary to read all the drives in order to recalculate the parity, which must then be rewritten. Alternatively, it can read the old user data and the old parity data and recompute the new parity from them. Even with this optimization, a small update requires two reads and two writes.As a consequence of the heavy load on the parity drive, it may become a bottleneck. This bottleneck is eliminated in RAID level 5 by distributing the parity bits uniformly over all the drives, round robin fashion, as shown in Fig. 5-19(f). However, in the event of a drive crash, reconstructing the contents of the failed drive is a complex process.
参考资料：
modern operating system
其他类似问题
为您推荐：
您可能关注的推广
raid0的相关知识
等待您来回答
下载知道APP
随时随地咨询
出门在外也不愁侠盗猎车手4免安装汉化硬盘版的是什么版本的?顶上说是1.0的，是1.1.1.0，还是1.0.0.0？_百度知道
侠盗猎车手4免安装汉化硬盘版的是什么版本的?顶上说是1.0的，是1.1.1.0，还是1.0.0.0？
我要比较完整的回答，应为要下对应的补丁！拜托了
下补丁下什么
要清楚点 最新的
提问者采纳
比如你要打1,也就是GTA4的资料片.如果你要升级.4升级补丁+3DM中文汉化1,游戏版本是1,汉化是1,没有必要一个一个的打.0。PS..0.7,那个是自由城故事,就不需要注册表了.4..上面还有教你如何还原成英文版的方法,所以最好下一个注册表还原文件,3DM论坛上有,推荐下载V1。你说的这个免安装汉化硬盘版我在游民星空上找到了,因为你这是免安装的,1.2的吧,直接打就好了,就能看出游戏是什么版本了.1.然后如果你觉的卡的话(打上中文补丁会卡)..0.0,网上也有..4升级后可以解决掉帧问题.还有GTA4没有1.5BETA版.0.4升级补丁的覆盖版。目前GTA4最多到1.如果你要玩中文版,或者你可以直接下载V1.0升级补丁呢.1,可以下载一个3DM中文不卡补丁.0的..其实你点游戏图标右键属性里有一个版本.0侠盗猎车手4要下补丁直接下需要的补丁就好了
提问者评价
其他类似问题
为您推荐：
您可能关注的推广
侠盗猎车手4的相关知识
其他1条回答
等待您来回答
下载知道APP
随时随地咨询
出门在外也不愁硬盘的SATA2，SATA3 是什么意思？我的主版上硬盘插口上标的是SATA 1 ，请问能换SATS3硬盘吗?
硬盘的SATA2，SATA3 是什么意思？我的主版上硬盘插口上标的是SATA 1 ，请问能换SATS3硬盘吗?
不区分大小写匿名
SATA2代 200M/S 3代300M/s 可以用SATA3硬盘，但是速度是SATA1 可能有兼容性问题。
硬盘接口是硬盘与主机系统间的连接部件,作用是在硬盘缓存和主机内存之间传输数据。不同的硬盘接口决定着硬盘与计算机之间的连接速度,在整个系统中,硬盘接口的优劣直接影响着程序运行快慢和系统性能好坏。从家用用户的角度出发,硬盘接口分为IDE、SATA两种规格,不过他们各自具有自身的优势和特点,用户需要根据自身的情况来加以选择。 IDE接口硬盘及主板接口

IDE接口硬盘一般就是我们俗称的并行规格的PATA硬盘,目前大多数台式存储系统采用的都是称为Ultra-ATA的并行总线接口硬盘产品,这样的规格技术是自80年代以来一直被应用在桌上型系统作为主流的内部储存互连技术,由于运用领域十分广泛时间又较长,所以成熟的技术带来的是大规模集成制造的低成本和飞速发展的大容量。
由于长时间的没有改变,在数据的传输上来看,这种IDE接口硬盘显得有一些滞后,因为目前主流的PATA硬盘仅能支持ATA/100和ATA/133两种数据传输规范,传输速率最高只能达到 每秒100或133MB,这仅可以满足目前一般情况下的大容量硬盘数据传输。另外,这类硬盘所使用的80-pin数据线在机箱内部杂而乱,它会阻碍空气在机箱里的流动,从而影响到系统的散热。虽然劣势明显,不过对于一些原来老用户来说,由于原有的主板平台并不支持SATA接口,这种IDE接口的PATA大容量硬盘还是首选,还有一些用户认为这类型的硬盘在技术上成熟、稳定,所以也选择这类型的PATA硬盘。
由英特尔、戴尔、希捷、Maxtor以及APT等厂商所组成serialata.org,推出了就硬盘而言的新技术规格,Serial ATA,它为串行接口,在IDF Fall 2001大会上,希捷宣布了Serial ATA 1.0标准,正式宣告了SATA规范的确立这也是硬件新近颁布的一种的标准。
在技术特点来看,不得不承认PATA硬盘在安装、传输速率及功耗、抗震、噪声等多方面都要逊于SATA硬盘。因为SATA硬盘它具有更快的外部接口传输速度,数据校验措施更为完善,SATA 1.0规范规定的标准传输率可以达到150MB/S,这样可以充分发挥Serial ATA接口的性能优势,因为ATA100的理论数值是100MB/s,即便是ATA133也最高为133MB/s。另外在安装上首先SATA的连接线非常方便,而且SATA最重要的特性就是支持热插拔。串行SATA方式通过更好的数据校验方式,信号电压低可以有效的减小各种干扰,从而大大提高数据传输的效率,而且新式的SATA硬盘连接线也更加有利机箱内部的散热。
SATA并非只有优点,在缺点上也是显而易见,由于SATA规格还不十分成熟,这种类型的硬盘对外频要求要比并行规格硬盘高,如果用户有超频的情况这时一定要注意,因为它就会常常出现找不到硬盘或数据损坏的情况。目前支持SATA 2.0的硬盘也已经推出,相信不久SATA 3.0也会出现在市场中,但并非标准越高就越好,就目前而言这种SATA2.0规范的硬盘主要还是针对服务器和网络存储应用,如普通消费者选择SATA 1.0规范的硬盘产品足以

一般PATA的硬盘传输速度有:
Ultra-ATA33
Ultra-ATA66
Ultra-ATA100
Ultra-ATA133
SATA硬盘传输速度有:
Ultra-ATA150
相关知识等待您来回答
硬件领域专家
& &SOGOU - 京ICP证050897号