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SAS hard drive Data recovery software free download
  • Author:urecovery
  • Publish Time:2018-09-17 09:24

SAS (Serial Attached SCSI) is a new generation of SCSI technology. It is the same as the popular Serial ATA (SATA) hard disk. It uses serial technology to achieve higher transmission speed and shortens the connection line. Improve interior space and more. SAS is a new interface developed after the parallel SCSI interface. This interface is designed to improve the performance, availability, and scalability of your storage system and provides compatibility with SATA drives. [1] 
SAS interface technology is backward compatible with SATA. Specifically, the compatibility between the two is mainly reflected in the compatibility between the physical layer and the protocol layer. At the physical layer, the SAS interface and the SATA interface are fully compatible. The SATA hard disk can be directly used in the SAS environment. From the interface standard, SATA is a sub-standard of SAS, so the SAS controller can directly control the SATA hard disk, but SAS However, it cannot be directly used in the SATA environment, because the SATA controller cannot control the SAS hard disk; at the protocol layer, the SAS consists of three types of protocols, and the corresponding protocols are used for data transmission according to different connected devices. The Serial SCSI Protocol (SSP) is used to transfer SCSI commands; the SCSI Management Protocol (SMP) is used to maintain and manage connected devices; and the SATA Channel Protocol (STP) is used to transfer data between SAS and SATA. Therefore, with these three protocols, SAS can be seamlessly integrated with SATA and some SCSI devices.
The SAS hard disk is the fastest in the mechanical hard disk. First, the SAS interface on the interface is faster than the SATA and SCSI mechanical hard disks. Secondly, the speed is fast and the seek is fast, so the SAS hard disk is applied to the diskless server for reading. Or write.
The back panel of the SAS system can be connected to a dual-port, high-performance SAS drive or a high-capacity, low-cost SATA drive. So SAS drives and SATA drives can exist in one storage system at the same time. However, it should be noted that the SATA system is not compatible with SAS, so the SAS drive cannot be connected to the SATA backplane. Due to the compatibility of the SAS system, users can use hard disks with different interfaces to meet the capacity or performance requirements of various applications. Therefore, when the storage system is expanded, it has more flexibility, so that the storage device can maximize the investment.
In the system, each SAS port can connect up to 16256 external devices, and SAS adopts direct point-to-point serial transmission mode, and the transmission rate is up to 3Gbps. It is estimated that there will be 6Gbps or even 12Gbps high-speed interfaces in the future. The SAS interface has also been greatly improved. It also provides 3.5-inch and 2.5-inch interfaces, so it can be adapted to different server environments. SAS relies on SAS expanders to connect more devices. SAS expanders are mostly 12-port. However, according to the board manufacturer's product development plan, there will be 28 and 36-port expanders introduced to connect SAS devices and host devices. Or other SAS expanders.
Compared with the traditional parallel SCSI interface, SAS not only significantly improves the interface speed (the mainstream Ultra 320 SCSI speed is 320MB/sec, while SAS has just started to reach 300MB/sec, and will reach 600MB/sec or more in the future). Moreover, due to the use of a serial cable, not only can a longer connection distance be achieved, but also anti-interference ability can be improved, and the thin cable can also significantly improve the heat dissipation inside the chassis.
The shortcomings of SAS mainly include the following aspects:
1) There are few types of hard disks and control chips: Only a few hard disk manufacturers such as Teke Core, Seagate, Maxtor, and Fujitsu have introduced SAS interface hard disks, and the variety is too small. Most of the SAS hard disks of other manufacturers are in the internal testing stage of the products. In addition, there are not many types of SAS controller chips or some SAS riser cards in the vicinity, and most of them are concentrated in the hands of LSI and Adaptec.
2) The price of the hard disk is too expensive: the SAS hard disk is more than doubled compared to the Ultra 320 SCSI hard disk of the same capacity. The price that has always been high has directly affected the number of users' purchases and the amount of channels digested, and it is unable to form a large-volume SAS hard disk, and the cost pressure will in turn cause the price to fall. If you want to make a simple RAID level, you not only need to buy multiple SAS hard drives, but also expensive RAID cards, the price is basically the same as the hard drive.
Detailed SAS
3) The actual transmission speed does not change much: the interface speed of the SAS hard disk does not represent the data transmission speed, and is limited by the mechanical structure of the hard disk. The mechanical structure of the SAS hard disk is almost the same as that of the SCSI hard disk. The bottleneck of data transmission is concentrated on the internal data transmission speed of the hard disk determined by the internal mechanical mechanism of the hard disk and the hard disk storage technology and the disk rotation speed, that is, about 80 MBsec, and the performance improvement of the SAS hard disk is not obvious.
4) Users pursue mature and stable products: From the perspective of products that have already been launched, SAS hard disks are more widely used in high-end 4-way servers, and server users with more than 4 channels are not blindly pursuing high-speed hard disk interface technology. They should be mature and stable hardware products. Although the SAS interface server and SCSI interface products are similar in speed and stability, the technology and products are not mature enough.
However, with the promotion of motherboard chipset manufacturers such as Intel, hard disk manufacturers such as Seagate and many server manufacturers, SAS related product technology will gradually mature, and prices will gradually decline, and sooner or later will become the mainstream interface of server hard disks.
At this stage, it has become the mainstream interface of cloud server service providers.
Two SAS 300G hard disk failure data recovery records
The customer uses two disks to form a raid0, one of which lights up in yellow. After being kicked out by the raid card, the raid crashes. The following highlights the situation of the rescue data at that time.
       The hard disk used by the customer is two SAS 300Gs. The hard disk is first unplugged from the machine, and then directly connected to the win environment through the SAS HBA, and the hard disk is marked as offline in the disk management to ensure the operation process. Medium is read-only and protects the security of the original data.
After mirroring all the sectors on the bottom of the two hard disks, the file system analyzes the disk order and stripe size, and uses the software virtual reorganization to set up the original raid environment. After further parsing the ntfs file system, the data is finally seen. At this time, new problems have arisen. After copying the data directly, the original system and application need to be redeployed, and because there is no support from the software service provider, it is not easy to implement, so I want to put it up. The raid is completely migrated to the new raid environment, and it can be done the same as before the damage. Save a lot of time.
For the new raid environment customers learned the lesson, decided to use three disks to build raid5, so even if a disk is offline, the raid can be in a downgrade state, will not crash immediately, giving users the opportunity to replace the new hard disk.
I created a raid5 volume after installing a new raid card that supports raid5 and plugged in a new hard disk. Now I am going to study how to migrate the data I have made.
Because the front panel of the server is managed by the raid card, it is not directly recognized by the system directly after inserting a new disk. It needs to be created after the raid is created under the raid card, and is limited to the single disk capacity. The program then studied other methods. Because the server front panel has a DVD drive, and now the server optical drive and motherboard are connected by sata channel, so you can open the cover using the sata port, connect a sata hard drive, in pe or linux live cd mode The data is moved back, and this is the fastest way. But when we are ready to implement, we find that the sata used by this machine is not a standard size interface type, but a mini sata, because there is no ready-made adapter card in hand, so this method is not good, in fact, when the amount of data is not large, Use the USB method to do it, but because most of the server's usb still stays at USB2.0 too slowly, it is unacceptable for large data volume.
In the end, we definitely use a novel way to move back the data---going the network.
At this time, we need to start a linux live cd. Generally we use linux system rescue cd. After the linux boot is completed, ifconfig configures the server ip, then we will put the data on a win 2008 r2 machine, in the win environment. Open nfs service (default is off) "Service Manager - Role - Add Role - Check File Service - Check Network File System Service to install, you need to restart the computer after the first installation is completed"
After the restart is complete, we operate the folder where the mirrored data is stored. Right-click the NFS share tab and select Share this folder. Then, the key point is to allow the root directory access in the permissions, and select the read and write access type.
After the Win side is set, we will look at the linux side settings, ifconfig view the current network configuration.
Because we need to assign an ip to him, here we assign the network card "enp4s0", the ip address is assigned to subnet mask is, use the following command: ifconfig enp4s0 and then use ifconfig View ip address
After configuring ip, check if the network is together. Command: ping
Then check whether the NFS shared directory on the machine is accessible. Command: showmount –e,
The source machine and the target machine are now connected, creating a directory mkdir /mnt/bysjhf in linux
After creation, we will mount the mirrored data to the newly created folder under Linux. mount /data /mnt/bysjhf –o nolock
After mounting, check the mount point information df –k
After confirming that it is mounted, go to this folder and check the image file in the folder:
Root@sysresccd /mnt/bysjhf % ls
And view the hard disk and partition information: fdisk –l
After confirming the source device and the target device, perform mirroring:
Dd if=/mnt/bysjhf/data.img of=/dev/sda bs=10M
In the Gigabit network environment, the speed of NFS can run to 70M/S. This is already an ideal speed. After waiting for dd to complete, we restart the ibm X3650 server and select raid boot. The expected windows startup page finally appears. The hard work in front of it was not in vain, and the complete migration of the data was successful.