Here is a summary of how to configure hard disks on Windows and Linux PC machines. It describes SAN and NAS.
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"JBOD" (Just a Bunch Of Disks) refers to hard disks that aren't configured according to a RAID subsystem of disk drives that improves performance and fault tolerance.
As of this writing, common capacities on for single hard drive mechanical devices range up to 750GB and 1+ Terrabytes (1000 GB).
This intelligence makes SCSI more expensive, since SCSI uses two processors — one for executing the commands and handling the interface and another processor controlling the head positioning through servos.
Ultra320 SCSIPCI Express replaces PCI and PCI-X on motherboards, and as a serial interconnect, provides high performance (multiple Gbps per connection) and scalability to networked storage systems.
SATA/IDE SATA (Serial ATA) also known as IDE was defined by the Serial ATA International Organization (SATA-IO) to be software compatible with Parallel ATA, which offer data rates of up to of 100 MB/s. SATA has a max. data transfer rate of 59 MBps through a single port. Serial ATA supports data rates up to 150 MB/s.
It uses ATA disks in a redundant array to provide mass, reliable storage inexpensively.
The new interface also provides for command queuing to further boost system performance.
SATA uses smaller cable connectors with improved silicon design for lower voltage that alleviates current design requirements in Parallel ATA from Seagate
SAS (Serial Attached SCSI) SAS (Serial Attached SCSI) began shipping in 2005 as Seagate and Maxtor Atlas 10K V and Atlas 15K II drives.
There are three major technologies:
iSCSI IETF RFC 3720 introduces complete error recovery mechanisms called Error Recovery Level Two (ERL 2)
In any SCSI connection there is at least one initiator and one target.
A Performance Comparison of NFS and iSCSI for IP-Networked Storage showed that iSCSI is faster than NFS because iSCSI caches and updates meta-data asynchronously and transfers blocks rather than files. here and Mathias Gug of CERN
NAS filers are sometimes called NAS "heads" because the NAS "node" is referenced using the IP address of the head device.
Most NAS supports Multi-platform File Sharing by simultaneously supporting Windows Common Internet File System (CIFS) and Unix Network File System (NFS) as well as file systems associated with Macintosh, Novell, and other operating systems. This makes them ideal for sharing files across OS platforms on the same network.
CIFS was formerly known as Server Message Block (SMB) developed by IBM and Microsoft to support file sharing in DOS. This protocol is used today in UNIX systems as part of the Samba open-source utility package.
Many NAS systems also support HTTP so that clients can download files and administer the system using their Web browser.
Since NAS filers do not need a general-purpose operating system, they cost less, have less to go wrong. They also have less avenues of attack, which make them more secure than file servers.
Some NAS systems can expand into multiple terabytes. Non-scaling NAS systems need to be taken offline to redistribute data when adding capacity.
With a SAN, app servers access files contained in SAN storage using basic block I/O commands. just as if the storage were part of the server not by calling for files over a LAN.
Instead of a NIC card, servers access the SAN using an HBA (Host Bus Adapter) board to encode data per the fast & secure 8B/10B scheme that addresses SANs with a hard-coded 64-bit World Wide Name (WWN) and World Wide Port_Name (WWPN).
Although a SAN does not (usually) offer file sharing, it does offer storage sharing to servers. The storage sharing can be physical (with a fixed logical "wall" between servers that run different operating systems), or partitioned logical storage (shared by servers that run the same operating system).
Due to the high-speed (1 to 2Gb/s data transfer rates in 2006, and 10Gg/s in 2008), SANs usually run though a fiber channel (IEEE 802.2) networking equipment.
At the fabric layer, fibre technology provides sophisticated cascading switches, switch initialization, and zoning.
It is almost a mute point to compare the total costs of a SAN, since in may large/enterprise shops that need highly-available central consolidated data store for clusters of servers to access, it has become a "must-have" for its ability to handle large amounts of data quickly and securely at low per-byte hardware, power, and manpower cost.
For more information:
FREE vendor-neutral SAN Fundamentals 8-hour on-line class professionally developed and offered at HP since Feb. 2004
Fiber comes with advanced services such as
Fibre Channel technology are used on trans-oceanic cables (which have repeaters every 10km, powered by a copper sheath around the fiber.) But the HBA and devices can be up to 500m apart.
A series of standards from the American National Standards Institute (ANSI) defines 3 main topologies:
Transmits data in frames of 2148 bytes maximum.
PartitionsDrives using MBR technology can have up to 3 primary partitions, plus one extended partition.
Space on a physical disk not used by a primary partition can be used by the Extended Partition. The extended partition can be formatted for use by other operating systems (such as Linux). DOS divides the extended partition into smaller segments, each assigned a logical drive and formatted with a FAT file system.
Creating DisksTo create MBR partitions, run from a bootable floppy or the Win2000 setup CD:
For more on this topic, see:
boot partition holds the remainder of the operating system files.
Each Primary partition set as active contains boot files to start the operating system. Each OS has a different version of these hidden read-only system boot files:
Each parent folder contains subfolders such as System32, which holds the Windows Kernel kernel32.dll.
Windows 2000 can create "Dynamic Disks", then -without rebooting- resize, stripe, mirror, and RAID-5 them.How Fdisk works - step by step with sample screens
A Simple Dynamic volume on Windows 2000 may or MAY NOT have a partition table!
Troubleshooting Windows Messages
For the NT boot/system FAT partition: a single 2 GB FAT16 or NTFS partition.
FAT16 partitions are formatted at or below 2 GB using a 32K cluster size, or 4GB if partitioned by NT using a 64K cluster size. This avoids having any file beyond the 1024th cylinder during the installation of service packs. (See KB article Q197295).
Making this a FAT16 partition allows a DOS floppy to be used in booting up the system when recovering from problems with NT. Because FAT partitions are not secure, there should be no public shares on this volume.
The BIOS int13H disk I/O function calls interface limits the system partition to 7.8GB size IF you first partition and format it as NTFS on another PC and move the HD to the system you want to install NT to -- per KB Q119497.
Plus, a partition formatted NTFS using Disk Administrator performs slightly better than one converted from FAT.
But there's a new ATAPI.SYS in SP4 that handles IDE drives larger than 8GB. Have it on a diskette during the install. KB Q197667 explains it and gives steps to install it during an initial NT setup.
For paging files, a single 2 GB FAT16 drive
Because of their volatility, paging data should not be mirrored.
FAT16 partitions are much faster than NTFS when used in write intensive situations. This is because the architecture of NTFS requires a duplicate copy of the Master File Table (MFT) to be placed in the middle of the drive partition to supplement the one that is at the beginning of the partition. When new data is written to a file it causes properties of the file object to change (such as the file size, the date the file was last changed, the user that last updated the file, and possibly the cluster allocation chain). This information must be updated on both copies of the MFT. This causes a large amount of head swing since the second copy is in the center of the partition.
For user data and applications, a RAID 5 array:
All total, this configuration requires seven drives at minimum. I do recommend that if you are going to reinstall your server to redo your disk configuration, that you install separate drives for the system volume and your RAID. There are dozens of valid choices about configuring your drives. You must weigh cost vs. required performance to arrive at the best solution.
For Exchange/SQL server log files: 2 GB FAT partitions which are hardware mirrored.
Exchange Server will operate in a Microsoft Cluster Server environment, but there are a bunch of problems. You may wish to check out some of the MSKB articles
If you use a cluster, turn off circular logging if you want a fairly clean backup.
Thanks to Tom Baffy on ZDU
$125 R-Studio from R-TT.COM claims to be the most comprehensive data recovery solution for FAT12/16/32, NTFS, NTFS5, and Ext2FS. It recovers data both on local logical and physical disks -- including encrypted files, compressed files on RAID drives -- even if their partition structures are damaged or deleted. Their $180 network edition recovers disks on remote computers over networks. R-Mail from R-TT.COM recovers corrupted *.dbx files where MS Outlook Express 5.0/ 5.01/5.5/6.0 store folders with messages. The new e-mail recovery technology allows the users to rebuild corrupted *.dbx files and restore accidentally deleted messages. The messages are recovered in the .eml format and can be imported into Outlook Express mail bases.
These utilities clean residual data on hard drives:
On Jan 21, 2002 Kurt Seifried announced that windows file wiping utilities do not wipe alternate data streams with NTFS file systems: In the NTFS file system a facility exists to bind additional data to a file or directory, called an alternate data stream [url1][url2]. These alternate data streams cannot be be removed, unless the parent file or directory is destroyed. Unfortunately most file wiping utilities only deal with the primary data stream and do not wipe the alternate data streams, thus leaving data intact.
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