operatingsystem操作系统ch12massstoragesystems49.ppt

上传人:p** 文档编号:465168 上传时间:2023-09-07 格式:PPT 页数:48 大小:584.50KB
下载 相关 举报
operatingsystem操作系统ch12massstoragesystems49.ppt_第1页
第1页 / 共48页
operatingsystem操作系统ch12massstoragesystems49.ppt_第2页
第2页 / 共48页
operatingsystem操作系统ch12massstoragesystems49.ppt_第3页
第3页 / 共48页
operatingsystem操作系统ch12massstoragesystems49.ppt_第4页
第4页 / 共48页
operatingsystem操作系统ch12massstoragesystems49.ppt_第5页
第5页 / 共48页
operatingsystem操作系统ch12massstoragesystems49.ppt_第6页
第6页 / 共48页
operatingsystem操作系统ch12massstoragesystems49.ppt_第7页
第7页 / 共48页
operatingsystem操作系统ch12massstoragesystems49.ppt_第8页
第8页 / 共48页
operatingsystem操作系统ch12massstoragesystems49.ppt_第9页
第9页 / 共48页
operatingsystem操作系统ch12massstoragesystems49.ppt_第10页
第10页 / 共48页
亲,该文档总共48页,到这儿已超出免费预览范围,如果喜欢就下载吧!
资源描述

《operatingsystem操作系统ch12massstoragesystems49.ppt》由会员分享,可在线阅读,更多相关《operatingsystem操作系统ch12massstoragesystems49.ppt(48页珍藏版)》请在第壹文秘上搜索。

1、12.2nOverview of Mass Storage StructurenDisk StructurenDisk AttachmentnDisk SchedulingnDisk ManagementnSwap-Space ManagementnRAID StructurenDisk AttachmentnStable-Storage ImplementationnTertiary Storage DevicesnOperating System IssuesnPerformance Issues12.3nDescribe the physical structure of seconda

2、ry and tertiary storage devices and the resulting effects on the uses of the devicesnExplain the performance characteristics of mass-storage devicesnDiscuss operating-system services provided for mass storage,including RAID and HSM12.4nMagnetic disks provide bulk of secondary storage of modern compu

3、terslDrives rotate at 60 to 200 times per secondlTransfer rate is rate at which data flow between drive and computerlPositioning time(random-access time)is time to move disk arm to desired cylinder(seek time)and time for desired sector to rotate under the disk head(rotational latency)lHead crash res

4、ults from disk head making contact with the disk surface4Thats badnDisks can be removablenDrive attached to computer via I/O buslBusses vary,including EIDE,ATA,SATA,USB,Fibre Channel,SCSIlHost controller in computer uses bus to talk to disk controller built into drive or storage array12.512.6nMagnet

5、ic tapelWas early secondary-storage mediumlRelatively permanent and holds large quantities of datalAccess time slowlRandom access 1000 times slower than disklMainly used for backup,storage of infrequently-used data,transfer medium between systemslKept in spool and wound or rewound past read-write he

6、adlOnce data under head,transfer rates comparable to diskl20-200GB typical storagelCommon technologies are 4mm,8mm,19mm,LTO-2 and SDLT12.7nDisk drives are addressed as large 1-dimensional arrays of logical blocks,where the logical block is the smallest unit of transfer.nThe 1-dimensional array of lo

7、gical blocks is mapped into the sectors of the disk sequentially.lSector 0 is the first sector of the first track on the outermost cylinder.lMapping proceeds in order through that track,then the rest of the tracks in that cylinder,and then through the rest of the cylinders from outermost to innermos

8、t.12.8nHost-attached storage accessed through I/O ports talking to I/O bussesnSCSI itself is a bus,up to 16 devices on one cable,SCSI initiator requests operation and SCSI targets perform tasks lEach target can have up to 8 logical units(disks attached to device controllernFC is high-speed serial ar

9、chitecturelCan be switched fabric with 24-bit address space the basis of storage area networks(SANs)in which many hosts attach to many storage unitslCan be arbitrated loop(FC-AL)of 126 devices12.9nNetwork-attached storage(NAS)is storage made available over a network rather than over a local connecti

10、on(such as a bus)nNFS and CIFS are common protocolsnImplemented via remote procedure calls(RPCs)between host and storagenNew iSCSI protocol uses IP network to carry the SCSI protocol12.10nCommon in large storage environments(and becoming more common)nMultiple hosts attached to multiple storage array

11、s-flexible12.11nThe operating system is responsible for using hardware efficiently for the disk drives,this means having a fast access time and disk bandwidth.nAccess time has two major componentslSeek time is the time for the disk are to move the heads to the cylinder containing the desired sector.

12、lRotational latency is the additional time waiting for the disk to rotate the desired sector to the disk head.nMinimize seek timenSeek time seek distancenDisk bandwidth is the total number of bytes transferred,divided by the total time between the first request for service and the completion of the

13、last transfer.12.12nSeveral algorithms exist to schedule the servicing of disk I/O requests.nWe illustrate them with a request queue(0-199).98,183,37,122,14,124,65,67Head pointer 5312.13Illustration shows total head movement of 640 cylinders.12.14nSelects the request with the minimum seek time from

14、the current head position.nSSTF scheduling is a form of SJF scheduling;may cause starvation of some requests.nIllustration shows total head movement of 236 cylinders.12.1512.16nThe disk arm starts at one end of the disk,and moves toward the other end,servicing requests until it gets to the other end

15、 of the disk,where the head movement is reversed and servicing continues.nSometimes called the elevator algorithm.nIllustration shows total head movement of 208 cylinders.12.1712.18nProvides a more uniform wait time than SCAN.nThe head moves from one end of the disk to the other.servicing requests a

16、s it goes.When it reaches the other end,however,it immediately returns to the beginning of the disk,without servicing any requests on the return trip.nTreats the cylinders as a circular list that wraps around from the last cylinder to the first one.12.1912.20nVersion of C-SCANnArm only goes as far as the last request in each direction,then reverses direction immediately,without first going all the way to the end of the disk.12.2112.22nSSTF is common and has a natural appealnSCAN and C-SCAN perfo

展开阅读全文
相关资源
猜你喜欢
相关搜索

当前位置:首页 > 高等教育 > 大学课件

copyright@ 2008-2023 1wenmi网站版权所有

经营许可证编号:宁ICP备2022001189号-1

本站为文档C2C交易模式,即用户上传的文档直接被用户下载,本站只是中间服务平台,本站所有文档下载所得的收益归上传人(含作者)所有。第壹文秘仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对上载内容本身不做任何修改或编辑。若文档所含内容侵犯了您的版权或隐私,请立即通知第壹文秘网,我们立即给予删除!