Questions tagged [scsi]

Small Computer System Interface (SCSI, pronounced skuz-ee) is a set of parallel interface standards developed by the American National Standards Institute (ANSI) for physically connecting and transferring data between computers and peripheral devices(like printers, disk drives, scanners and other). It is a fast bus and supported by all major operating systems.

Small Computer System Interface (SCSI, pronounced skuz-ee) is a set of standards for physically connecting and transferring data between computers and peripheral devices. The official name of the SCSI standard is: ANSI X3.131.

The SCSI standards define commands, protocols, and electrical and optical interfaces. SCSI uses a low-voltage differential (LVD) bus, a method where data is transmitted by comparing the difference in voltage between a pair of wires. SCSI is most commonly used for hard disks and tape drives, but it can connect a wide range of other devices, including scanners and CD drives.

Some important features:

  • SCSI is capable of supporting eight devices, or sixteen devices with Wide SCSI.
  • The latest version, 16-bit Ultra-640 (Fast-320) SCSI has a 640 MBps transfer speed.
  • SCSI standards are generally backward-compatible.

Common SCSI components:

  • Initiator - it issues requests for service by the SCSI device and receives responses.
  • Target - A SCSI target is typically a physical storage device like a hard-disk or a storage array
  • Service delivery subsystem - it allows communication to occur between the initiator and the target

The SCSI subsystem has a 3 level architecture with the "upper" level being closest to the user/kernel interface while the "lower" level is closest to the hardware.

For more info: http://en.wikipedia.org/wiki/SCSI

181 questions
30
votes
7 answers

How can I simulate a failed disk during testing?

In a Linux VM (Vmware workstation or similar), how can I simulate a failure on a previously working disc? I have a situation happening in production where a disc fails (probably a controller, cable or firmware problem). Obviously this is not…
MarkR
  • 62,604
  • 14
  • 116
  • 151
13
votes
2 answers

why is virtio-scsi much slower than virtio-blk in my experiment (over and ceph rbd image)?

Hi I recently did a experiment of virtio-scsi over rbd through qemu target (for its DISCARD/TRIM support), and compared the throughput and iops with that of a virtio-blk over rbd setup on the same machine, using fio in the guest. Turnout the…
Zhaohui Yang
  • 173
  • 1
  • 1
  • 7
6
votes
3 answers

How to find out if SCSI device (say /etc/sda) is a disk or not via ioctl calls or other?

How to find out if SCSI device (say /dev/sda) is a disk or not via ioctl calls or other ? I have tried the following but the ioctl call fails. My /dev/sda is a USB flash disk. #include #include #include #include…
clyfe
  • 23,695
  • 8
  • 85
  • 109
6
votes
2 answers

Retrieve SD Card Serial Number and Manufacturer under Linux

I want to be able to retrieve an SD Card's Serial Number, Manufacturer, and any other information it may provide. Java or just a command to run would be great. Compact Framework does it, but that doesn't help me.
Mark
  • 61
  • 1
  • 1
  • 2
6
votes
1 answer

SCSI Read (10) and Write (10) with the SCSI Generic Interface

I try to issue a scsi read(10) and write(10) to a SSD. I use this example code as a reference/basic code. This is my scsi read: #define READ_REPLY_LEN 32 #define READ_CMDLEN 10 void scsi_read() { unsigned char Readbuffer[ SCSI_OFF + READ_REPLY_LEN…
samuirai
  • 762
  • 1
  • 9
  • 25
6
votes
5 answers

Linux: writes are split into 512K chunks

I have a user-space application that generates big SCSI writes (details below). However, when I'm looking at the SCSI commands that reach the SCSI target (i.e. the storage, connected by the FC) something is splitting these writes into 512K…
Leonid99
  • 1,227
  • 2
  • 12
  • 10
5
votes
1 answer

Warning message when using a big disk and iscsi

There are two servers: Openfiler(v. 2.99) that exports a 5TB disk and Proxmox(v. 3.4) that uses this disk by iscsi-protocol. When using this disk I see in /var/log/syslog and dmesg-output the following message: kernel: sd 7: 0: 0: 0: [sde] Very big…
Борис
  • 165
  • 1
  • 6
5
votes
1 answer

SCSI Read10 vs Read16

Which case would be considered correct? Doing reads with a Read 16 command no matter if the LBA's are 32 or 64 bit. If the max LBA is 32 bit then do a Read 10 command and if the max LBA is 64 bit then do a Read 16 command. What are the pros and…
diggers3
  • 229
  • 3
  • 17
5
votes
1 answer

Is it possible to send SCSI commands to a USB device from within a kernel module?

Question How, given the information udev passes to my kernel module (the block device path maybe), can I send SCSI commands to the block device? (yet have it function normally otherwise, meaning partitions are mounted, no data loss, etc) What I'm…
5
votes
1 answer

Is there a definitieve resource that documents navigation of the linux /proc and /sys filesystems?

We use the /proc and /sys file systems in Linux to discover various types of system configuration information. Typically, we spelunk around through the different files and directories until we find the information that we need. I'm wondering if…
Steve Hawkins
  • 1,433
  • 4
  • 17
  • 24
4
votes
2 answers

VMWare Server: Virtual Hard Drive Type

For best performance, is it better to use a virtual IDE HDD or virtual SCSI HDD? If, SCSI, does it matter whether you use an BusLogic or LSILogic?
AndyM
  • 3,574
  • 6
  • 39
  • 45
4
votes
1 answer

SCSI read capacity (10) reports wrong LBA and sector size

I've been trying to test my AHCI driver for my hobby OS on bare metal. Before that, I tested my driver in QEMU with the parameters: qemu-system-i386 -boot d -cdrom elfboot.iso -machine q35 -m 2G -hda hda.img -serial stdio The output is something…
CRoemheld
  • 889
  • 7
  • 26
4
votes
4 answers

Sending a specific SCSI command to a SCSI device in Windows

Does windows have specific interface by which I can send a specific scsi command such Inquiry to scsi device ? I searched the net, found passing reference to SCSI Pass Through interface. But Its very Vague. Is there any documentation for that API…
Ganesh
  • 73
  • 1
  • 1
  • 5
4
votes
2 answers

Determine linux driver that owns a disk

I am trying to debug a situation where the SSD on my hardware is not being detected by the right device driver. The device driver that should own the SSD's is a software RAID driver (megasr) that will automically configure 2 SSD's in mirroring mode.…
4
votes
0 answers

Linux scsi command queue

I'm a newbie here at this forum. I'm currently stuck with a problem. I'm a beginner to Linux kernel drivers, and currently involved in developing a Linux SCSI device driver for a block mass storage device. The development platform is on a high-end…
ubermensch
  • 363
  • 2
  • 12
1
2 3
12 13