"For Prof. Goodman"
iram3408
discussion_67_and_8.docxDiscussion # 6
Message expanded. Message read RAID
posted by BRANDON MAZZONE, Mar 05, 2016, 7:41 PM
Raid (redundant array of independent disks) is the adopted industry standard way of organizing multiple storage disk arrays. The industry adopted these designs to provide a compatible storage option for multiple platforms. This Raid scheme is made up of 7 levels that are associated with their data format. These levels are not hierarchal but do share common characteristics. These characteristics include that the Operating system will see the array of physical drives as a single drive. Also data within the drives is shared amongst them. Another characteristic is that the drives are redundant to prevent a disk failure. I personally have a 4 solid state drive RAID array on my personal use computer. I like the way the drives function as one mass storage pool and i can access data from all the drives from one place.
posted by KERONE DIXON, Mar 05, 2016, 10:26 PM
RAID (redundant array of independent disks; originally redundant array of inexpensive disks) provides a way of storing the same data in different places (thus, redundantly) on multiple hard disks (though not all RAID levels provide redundancy). By placing data on multiple disks, input/output (I/O) operations can overlap in a balanced way, improving performance. Since multiple disks increase the mean time between failures, storing data redundantly also increases fault tolerance.
RAID arrays appear to the operating system (OS) as a single logical hard disk. RAID employs the technique of disk mirroring or disk striping, which involves partitioning each drive's storage space into units ranging from a sector up to several megabytes. The stripes of all the disks are interleaved and addressed in order.
Message expanded. Message read Re: RAID
posted by JOSEPH FISCHER, Mar 06, 2016, 9:19 AM
Raid 5 is the type of raid I see at my customer site. It gives them a good level of protection and it allows them to stay running should they have a singular disk failure. They are regularly monitoring their systems so they will normally catch the single fault and replace it quickly. If they happen to have a second failure before replacing the first though they are sunk.
http://www.raidrecoveryonline.com/raid10_vs_raid5/
Message expanded. Message read Re: RAID
posted by RICHARD BOHATY, Mar 06, 2016, 10:00 AM
Monitoring is the key, we had 2 go out on a raid 5 and discovered the 1st one had been alarming for 3 weeks :-( monitoring and good backups :-)
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Discussion # 7
Message expanded. Message read File Attributes
posted by ALICIA RANGEL, Mar 04, 2016, 9:29 PM
When a file is named it is for the users, benefit only. The computer does not operate off of the files name but does operate on its contents and coding or format. After the file is named the name typically stay with the file even when it is shared. The file becomes independent even when you send it in an email, add to a USB, or open in a software program. There are seven attributes that you should look for in a file name, identifier, type, location, size, protection, time, date, and user identification. The name that is given to the file is only for the user's identifying, as the computer looks for specifications and contents.
Message expanded. Message read Re: File Attributes
posted by JOSEPH FISCHER, Mar 05, 2016, 11:14 AM
File attributes can be tricky. Lately our customers that use EMC based storage often present us problems as EMC offers what are known as" extended attributes". These advanced attributes not used by standard operating systems and if they are present we are unable to properly archive a file. They need to be removed first.
http://www.emc.com/collateral/TechnicalDocument/docu55346.pdf
posted by JAMAR JOHNSON, Mar 05, 2016, 3:20 PM
Hi Alicia,
Thanks for the summary. What I thought was interesting about this section of the chapter was that it didn't make any mention of shared files. In the case of file sharing, both in-network and off-network, the circumstance would be slightly different. The name and attributes of the file would all stay the same, and only be for the benefit of the user, however the file wouldn't become independent. When users send a copy of a file over a network, through an e-mail, or save it a USB drive, they are essentially creating a copy. Whereas with a shared filed, all users are interacting with the same file on the disk. The Windows platform has its own support of this functionality which I used to find less than stellar, however Google Docs has become a common occurrence in my workplace.
Thanks, Jamar
posted by RICHARD BOHATY, Mar 06, 2016, 7:36 AM
Inherited permissions can be tricky; many OSs have "show effective permissions" to rapidly evaluate what permissions a specific user(s) has to an object.
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Discussion # 8
Message expanded. Message read File operations
posted by ALICIA RANGEL, Mar 04, 2016, 11:55 PM
There are six basic file operations create, write, read, repositioning, deleting, and truncating. To create a file, you must do two things check for space on the hard drive and an entry in the directory must be made for the new file. To write a file you make a system call and create a name and the data to be written to the file. To read from a file you call the system to find a name and where in the memory should the next block be put. Repositioning is when the system searches for an entry and the file position pointer is repositioned to a value.
posted by RICHARD BOHATY, Mar 05, 2016, 6:47 AM
Your post is right on. I ran into an application just this week that when installing would error out. In researching the application, we found out that the application did not do a space check when creating the install log. We contacted the vendor and they updated their installer.
posted by CHRISTINA RAY, Mar 05, 2016, 5:10 PM
I like the way you broke this down, it was an interesting chapter and the breaking it down sure helps. I find it amazing how smart these systems are, but they really just want the basic information so they can process it. More information is almost too much for the system but more for the end user, the end user is unable to read all the data in the backend.
posted by KERONE DIXON, Mar 05, 2016, 11:12 PM
The OS provides systems calls to create, write, read, reset, and delete files. The following discusses the specific duties an OS must do for each of the file operations.
Creating A space in the file system must be found for the file. Second, an entry for the new file must be made in the directory. The directory entry records the name of the file and the location in the file system.
Writing To write a file, a system call is made specifying both the name and the file and the information to be written to the file. Given the name of the file, the system searches the directory to find the location of the file. The directory entry will need to store a pointer to the current block of the file (usually the beginning of the file). Using this pointer, the address of the next block can be computed where the information will be written. The write pointer must be updated - in this way, successive writes can be used to write a sequence of blocks to the file.
Reading To read a file, a system call is made that specifies that specifies the name of the file and where (in memory) the next block of the file should be put. Again, the directory is searched for the associated directory entry, and the directory will need a pointer to the next block to be read. Once the block is read, the pointer is updated.
Resetting The directory is searched for the appropriate entry, and the current file position is reset to the beginning of the file.
Deleting To delete a file, the directory is searched for the named file. Having found the associated directory entry, the space allocated to the file is released (so it can be reused by other files) and invalidates the directory entry
The five operations that are described comprise only the minimal set of required file operations. More commonly, we shall also want to edit the file and modify its contents. A special case of editing a file is appending new information at the end of the file. Copies of the file can also be created, and since files are named object, renaming an existing file may also be needed. If the file is a binary object format, we may also want to execute it. Also of use are facilities to lock sections of an open file for multi process access, to share sections, and even to map sections into memory or virtual-memory systems.
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