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Topic: Rotational delay

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	Rotation Diet -- Recommendations and Resources (Site not responding. Last check: 2007-10-25)
		One consequence of the rotation of a planet is the phenomenon of precession.
		Old intro: The rotation of a body is the movement (or turning) of that body around a line, known as the axis, which runs through the body and is perpendicular to the direction of rotational motion.
		The term "rotated" (''to rotate, rotated, rot'd, rotation, and rotazn) is an increasingly popular term used by the Internet Subculture as a new term for "pwn" meaning to point out the defeat or loss of an opponent.
	www.becomingapediatrician.com /health/127/rotation-diet.html (831 words)

	[No title]
		Rotational speed indicates the speed at which the disks rotate, usually measured in revolutions per minute, rpm.
		Rotational speed may also be give as the time per one revolution, usually measured in milliseconds, ms.
		Rotational delay, or latency, is a measure of the average time that the device must wait for the correct record to reach the read-write heads.
	www.ric.edu /schaefer/CS310/Storage/Disks/DiskCharacteristics.doc (559 words)

	rotational latency - Webopedia.com
		Also called rotational delay, the amount of time it takes for the desired sector of a disk (i.e., the sector from which data is to be read or written) to rotate under the read-write heads of the disk drive.
		The average rotational latency for a disk is half the amount of time it takes for the disk to make one revolution.
		The term typically is applied to rotating storage devices, such as hard disk drives and floppy drives (and even older magnetic drum systems), but not to tape drives.
	itmanagement.webopedia.com /TERM/R/rotational_latency.html (97 words)

	Manual page for mkfs_ufs(1M)
		The rotational speed of the disk, in revolutions per second.
		The value is used to decide how much rotational spacing to place between successive blocks in a file.
		The maximum number of blocks, belonging to one file, that will be allocated contiguously before inserting a rotational delay.
	www.cs.utk.edu /~cs460.is&r/cgi-bin/group4/collection/mkfs_ufs.1m.html (688 words)

	CS 4432 Homework SOLUTION (Site not responding. Last check: 2007-10-25)
		This can be done while the buffer is still active elsewhere, hence effectively seek and rotational delay times can be reduced to zero.
		Reading each block is equal in time to the sum of average seek time + average rotational delay + transfer rate per block.
		The average seek time is 10 milliseconds, average rotational latency is 5 milliseconds, and average transfer time is 0.1 millisecond per block.
	www.cs.wpi.edu /~cs4432/d04/homework/hw1.sol.html (1722 words)

	Latency Article, Latency Information (Site not responding. Last check: 2007-10-25)
		On the other hand, the control system for the brakes on a car only needs to send a little bit of information (on or off), but that informationneeds to be sent with the shortest delay possible.
		While this is not a problem with non-digital instruments, devicesconnected to a computer always have some delay in the signal path.
		See also rotational delay and access time, which are other forms of latency.
	www.anoca.org /time/throughput/latency.html (483 words)

	Latency
		For most operations, such as transferring files on your computer, throughput is the most important measure, because such operations aren't complete until all of the data has been transferred.
		While this is not a problem with non-digital instruments, devices connected to a computer always have some delay in the signal path.
		See also rotational delay, which is another form of latency.
	www.brainyencyclopedia.com /encyclopedia/l/la/latency.html (497 words)

	765paper
		It is the waiting time for the desired block to rotate under the disk head; it is the time required for half a rotation on average, and is usually less than seek time [11].
		If the disk platters rotate at 5400 rpm, the time required for a rotation is the maximum rotational delay = (1 / 5400) * (60) = 0.011 seconds.
		The average rotational delay is half of the rotation time, (0.011 / 2) = 0.006 seconds.
	www.cs.ndsu.nodak.edu /~patel/765paper.html (2746 words)

	[No title] (Site not responding. Last check: 2007-10-25)
		rotational delay = (60 * 1000) / 7200 msec.
		rotational delay + time taken to transfer 50 contiguous blocks from outermost tracks) total no. of blocks for file = 9260 no.
		Rotational Delay = (1/8400) * (60 * 1000) msec = 7.14 msec Transfer Time for 250 Blocks = 7.14 msec Therefore Transfer Time for 1 Block = 7.14/250 msec A.
	www.csse.monash.edu.au /courseware/cse3000/hw/HW1Solutions.doc (1069 words)

	Rotational delay -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-25)
		Rotational delay -- Facts, Info, and Encyclopedia article
		Not usually applied to (A mechanism that transport magnetic tape across the read/write heads of a tape playback/recorder) tape drives, even though they rotate.
		There are other delays associated with accessing rotating media: ((computer science) the time it takes for a read/write head to move to a specific data track) seek time.
	www.absoluteastronomy.com /encyclopedia/r/ro/rotational_delay.htm (210 words)

	Delay systems (from explosive) -- Encyclopædia Britannica
		Delay, or rotational, shooting has many advantages over instantaneous firing in almost all types of blasting.
		For these, and sometimes other reasons, most blasting operations are now conducted with a delay system.
		More results on "Delay systems (from explosive)" when you join.
	www.britannica.com /eb/article-82385?tocId=82385 (932 words)

	2.2 Reducing Rotational Delay
		As we reduce the average seek distance, the rotational delay starts to dominate the disk access cost.
		To address this limitation, we replicate data at different rotational positions, and by choosing a replica that is rotationally closest to the disk head, we can reduce rotational delay.
		Replication for reducing rotational delay can increase seek distance by pushing data farther apart.
	www.usenix.org /events/osdi00/full_papers/yugum/yugum_html/node4.html (411 words)

	CIS 307: Files and all that
		We can do little to reduce the rotational delay [we may use disk scheduling, or use multiple heads, or improve sequential accesses, or...].
		Unless we use very big blocks, the transfer time is much smaller than the the seek and rotational delays.
		The key idea of the log-structured file system is to delay writes so that they can be made in big chunks, called segments, that include data blocks, index blocks, directory blocks, inodes, and inode list blocks (all inode list blocks are accessible from a single fixed location on disk).
	www.cis.temple.edu /~ingargio/old/cis307s96/readings/files.html (3245 words)

	PART C
		Consider a disk with an average seek time of 10ms, average rotational delay of 5ms, and a transfer time of 1ms for a 4K page.
		Assume that the cost of reading/writing a page is the sum of these values (i.e., 16ms) unless a sequence of pages is read/written.
		In this case the cost is the average seek time plus the average rotational delay (to find the first page in the sequence) plus 1ms per page (to transfer data).
	www.cs.cornell.edu /courses/cs432/2000fa/second-prelim-sample.htm (272 words)

	Better than RAID.. (fwd)
		The key contributions of this paper are: a flexible strategy for configuring disk arrays and its performance models, a software-only disk head position prediction mechanism that enables a range of position-sensitive scheduling algorithms, and evaluation of a range of alternative strategies that trade capacity for performance.
		More specifically, we present a disk array configuration, called an SR-Array, that flexibly combines striping with rotational replication to reduce both seek and rotational delay.
		This mechanism is not only a crucial ingredient in the success of the SR-Array configurations, it also enables the implementation of rotational position sensitive scheduling algorithms, such as Shortest Access Time First (SATF) [14,23], across the disk array.
	www.beowulf.org /archive/2001-July/004313.html (762 words)

	[No title] (Site not responding. Last check: 2007-10-25)
		Rotational Delay The time it takes for the heads to move to another cylinder.
		Balance of memory to store the block of data and the amount of space that is wasted on disk block sizes are too small.
		Rotational Delay — The time delay until the data to be transferred rotates into position under the read/write heads.
	www.cba.nau.edu /lorents-a/CIS410/l&mch11.doc (2060 words)

	CISC 235 Assignment 4 Sample Solution: disk timing (Site not responding. Last check: 2007-10-25)
		Note: take initial rotational delay, initial seek, and cylinder-to-cylinder (minimum) seek time into account.
		Answer: This is one random (average) seek and rotational delay, followed by reading a whole cylinder, followed by 4999 instances of: seek to adjacent cylinder, read entire cylinder.
		Initial random seek and rotational delay: 10+5 = 15ms.
	www.qucis.queensu.ca /home/dalamb/235/disksoln.html (516 words)

	Manual page for newfs(1M)
		It is used to decide how much rotational spacing to place between successive blocks in a file.
		The file system can either be instructed to try to minimize the time spent allocating blocks, or to try to minimize the space fragmentation on the disk.
		For a 4K file system, the default is 14; for an 8K file system, the default is 7.
	www.cs.utk.edu /~cs460.is&r/cgi-bin/group4/collection/newfs.1m.html (727 words)

	Sarah's Excellent Adventures in Solaris
		The maximum number of logical blocks contiguously laid out on disk for a UFS filesystem before inserting a rotational delay.
		The value for rotational delay has been obsoleted in Solaris 10 and Solaris 9 9/04 and defaults to 0 now, ensuring contiguous allocation.
		The device that hosts the filesystem will be queried as to the maximum transfer size it can handle, and the UFS I/O transfer size will default to this, if this information is obtainable.
	blog.sun.com /roller/page/sarahsblog?entry=inquiring_minds_want_to_know (693 words)

	[No title]
		On average, the rotational delay is half a revolution, or about 6ms.
		In many circumstances, rotational delay can be much less than the average.¡HZ# '#u#ó¨#Details of disc speedTransfer Time¡ $(¨· Once the data we want is under the read/write head, it can be transferred.
		The transfer time is given by the formula: Transfer time = number of bytes transferred X rotation time number of bytes on a track If a disc is sectored, the transfer time for one sector depends on the number of sectors on a track.
	www.bridgeport.edu /sed/draftcourses/cpe408_cs503/Lectures/Lecture7.ppt (1756 words)

	[No title]
		Explain the terms seek time, rotational delay, and transfer time.
		Time to access (read/write) a disk block: seek time: time to move disk heads to track on which desired block is located rotational delay: waiting for block to rotate under disk head; it is the time required for half a rotation on average, and is usually less than seek time.
		> If the disk platters rotate at 5,400 rpm, the time required for a rotation, which is the maximum rotational delay, is: (1/5400) x 60 = 0.011 seconds The average rotational delay is half of the rotation time, 0.006 seconds.
	longwood.cs.ucf.edu /~lisetti/teaching/courses/cop4710/chapter7.ppt (1637 words)

	Chang, E.; Chen, Y.: Minimizing Memory Requirements in Media Servers (Site not responding. Last check: 2007-10-25)
		This study explores the temporal and spatial relationships among concurrent media streams.
		Specifically, we propose adding proper delays to space out IOs in a media server to give more room for buffer sharing among streams.
		Memory requirements can be reduced by trading time for space.
	dbpubs.stanford.edu:8090 /pub/1996-4 (250 words)

	CIS 570 Homework 2 (Site not responding. Last check: 2007-10-25)
		Capacity: 1280 MB (1.2 GB) Minimum seek time: 1 ms (track to track) Average seek time: 10 ms Maximum seek time: 21 ms (full track) Spindle speed: 5,400 RPM Average rotational delay: 5.56 ms Max transfer rate: 16.7 MB/sec Bytes per sector: 512 Sectors per track: not specified Tracks per cylinder: 2 Cylinders: 6,569
		(5 pts) Compute the average rotational delay (latency) for this disk.
		latency is 1/2 the rotation time rotation time must be computed: 7200 rev 1 rev -------- = ----- ==> 7200 * x = 60 60 sec x sec x = 60/7200 =.0833 sec = 8.33 msec latency =.5 * 8.33 = 4.17 msec
	www.cse.ohio-state.edu /~lohse/CIS570/HWSp01/hw2ans.html (1379 words)

	dBforums - Re: [Testperf-general] Re: ExclusiveLock
		> offsets that might reduce the rotational delay.
		> > offsets that might reduce the rotational delay.
		> > > offsets that might reduce the rotational delay.
	www.dbforums.com /t1065554.html (967 words)

	Storage Devices
		Also, if you need low latency, faster drives are better; not only do they usually have lower average seek times, but also the rotational delay is one place where slow-spinning drives can never beat a faster one.
		(The average rotational latency is half the time it takes to rotate the drive once; thus, it is 2 milliseconds for 15,000RPM, 3ms for 10,000RPM drives, 4.2ms for 7,200RPM drives and 5.6ms for 5,400RPM drives.) Latency is seek time plus rotational delay.
		Make sure you understand whether you need low latency or more accesses per second, though; in the latter case (e.g., news servers), it may not be optimal to purchase one big fast drive.
	www.freebsd.org /doc/en_US.ISO8859-1/articles/storage-devices/article.html (11145 words)

	Trading Capacity for Performance in a Disk Array1
		A variety of performance-enhancing techniques, such as striping, mirroring, and rotational data replication, exist in the disk array literature.
		Given a fixed budget of disks, one must intelligently choose what combination of these techniques to employ.
		In this paper, we present a way of designing disk arrays that can flexibly and systematically reduce seek and rotational delay in a balanced manner.
	www.cs.princeton.edu /~rywang/papers/osdi00/MimdRAID/mimdraid.html (137 words)

	hw8 (Site not responding. Last check: 2007-10-25)
		What is the average rotational delay rd in msec?
		double buffering to save seek time and rotational delay.
		average rotational delay rd = (time for one disk revolution in msec) / 2 = 25 / 2
	www.mathcs.sjsu.edu /faculty/sathaye/hwch5a6sol.htm (4011 words)

	What is rotational latency? - A Word Definition From the Webopedia Computer Dictionary
		ProtoCAM: Rotational Molding Packaging Equipment - Provides rapid prototyping, manufacturing engineering consulting, SLA, and precision short-run production for urethane-based and investment castings.
		GlobalSpec: Rotational Molding - Engineering search engine for technical information on rotational molding companies.
		Fujitsu Allegro 6 (MAJ3182MC) 18.2 GB Hard Drive
	www.webopedia.com /TERM/R/rotational_latency.html (166 words)

	Study Guide Chapter 11
		How are pixels and dot pitch related to the resolution
		How the seek time and rotational delay are impacted by a fragmented disk.
		RAID Levels 0 and 1 (what it means, not what are they)
	www.mc.maricopa.edu /~marquez/cis105/study_guide02.html (85 words)

	[No title]
		Unlike RAM, time to retrieve a disk page varies depending upon location on disk.
		Seek time varies from about 1 to 20msec Rotational delay varies from 0 to 10msec Transfer rate is about 1msec per 4KB page Key to lower I/O cost: reduce seek/rotation delays!
		Two main techniques: Data striping: Data is partitioned; size of a partition is called the striping unit.
	www.mtholyoke.edu /courses/dstrahma/cs341/myslides/Ch9_Disks_Files-95.ppt (997 words)

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