From bcf74cdd7bf66c11f6b1b59315bc842aa5a649be Mon Sep 17 00:00:00 2001 From: Vladislav Bolkhovitin Date: Fri, 10 Jun 2011 01:43:05 +0000 Subject: [PATCH] Web and docs updates git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@3563 d57e44dd-8a1f-0410-8b47-8ef2f437770f --- qla2x00t/doc/qla2x00t-howto-debian.html | 356 ++++++++++++++++++ .../qla2x00t-howto.html | 0 www/comparison.html | 158 ++++---- www/downloads.html | 6 +- www/index.html | 1 + www/mc_s.html | 1 + www/scstvslio.html | 119 ++++++ www/scstvsstgt.html | 7 +- 8 files changed, 555 insertions(+), 93 deletions(-) create mode 100644 qla2x00t/doc/qla2x00t-howto-debian.html rename qla2x00t/{qla2x00-target => doc}/qla2x00t-howto.html (100%) create mode 100644 www/scstvslio.html diff --git a/qla2x00t/doc/qla2x00t-howto-debian.html b/qla2x00t/doc/qla2x00t-howto-debian.html new file mode 100644 index 000000000..b0bb52a4d --- /dev/null +++ b/qla2x00t/doc/qla2x00t-howto-debian.html @@ -0,0 +1,356 @@ + + + + + How to build and configure QLogic target driver for 22xx/23xx/24xx/25xx adapters on Ubuntu/Debian + + + +
+ +
How to build and configure QLogic target driver for 22xx/23xx/24xx/25xx adapters on Ubuntu/Debian. A Step by step guide.
+ +

+ +
+ Prerequisites: +
    +
  • Ubuntu/Debian 64bit base installation as minumum, fully updated.
    • +
  • Working internet/network connection from this installation (for apt).
    • +
  • Knowledge of configuring a Linux Kernel (a good base to work on is the configuration from the running kernel after installation)
    • +
  • Check if there are any patches for your kernel here
    • +
+
+ +
+
+ Note 1: I know this guide never builds a debian kernel package, i did not care about this, i only wanted to get the Generic SCSI Target Subsystem for Linux to work. I also know its not a good idea to compile anything as root, but again: i did not care about that either: the machine was a clean install, nobody will ever get hurt by me compiling a kernel or anything else as root. +
+
+ Note 2: I have to thank the original creator of this guide. I can not find your name but i can say i would not have been able to make it work wihtout it. I have based this document on that HowTo as a template.
+
+
+
ON TARGET
+ + +
ON INITIATOR
+ + +
ALL DONE, YOU SHOULD NOW HAVE A WORKING TARGET!
+
+ + \ No newline at end of file diff --git a/qla2x00t/qla2x00-target/qla2x00t-howto.html b/qla2x00t/doc/qla2x00t-howto.html similarity index 100% rename from qla2x00t/qla2x00-target/qla2x00t-howto.html rename to qla2x00t/doc/qla2x00t-howto.html diff --git a/www/comparison.html b/www/comparison.html index 2f66fce83..cd67cfff3 100644 --- a/www/comparison.html +++ b/www/comparison.html @@ -37,6 +37,7 @@

Comparison

@@ -51,7 +52,7 @@ mailing list and it will be corrected.

-

As on September 2010. Partially updated in December 2010.

+

As on June 2011.

@@ -60,7 +61,7 @@ @@ -69,7 +70,7 @@ + drivers (obsolete) @@ -80,22 +81,19 @@ - + - + @@ -129,7 +127,7 @@ transfer values (Wide (parallel) SCSI, SAS) +8 - + - + @@ -159,12 +157,12 @@ any target reconfiguration in a PnP-like manner) @@ -172,11 +170,11 @@ SCSI requirements 12 + + 12 - + @@ -228,11 +229,11 @@ to allocate too much memory for buffers and go into OOM state +apply changes in the config file on fly without any restarts + 13 @@ -243,19 +244,16 @@ apply changes in the config file on fly without any restarts - + - + - + @@ -273,11 +271,11 @@ apply changes in the config file on fly without any restarts - + +7 + 15 - + backend - + @@ -352,7 +348,7 @@ CD devices devices (VTL) - + @@ -374,10 +370,10 @@ devices (VTL) < @@ -418,38 +414,38 @@ target reconfiguration in a PnP-like manner) +reinstatement 18 +calculations, if available - + 13 - +
SCST STGT IET -LIO +LIO/TCM
Upstream kernel - Interface with in-kernel target - drivers - - - Since 2.6.38
Generic Target Engine + + iSCSI only + - Kernel only
Stability + + - 3 - + Probably (no released packages) Stability + + + Probably (no released packages)
Performance 4 ***** - 5 - *** **** **** - 6Performance 3 ***** + 4 + *** **** ****
Zero-copy passing data between target and backend drivers + - 7 + 5 + - 8 + 6 + +
+ -
Advanced devices access control -10 + - - + + - - +
Automatic sessions reassignment (changes in the @@ -145,10 +143,10 @@ resized through AENs or Unit Attentions (initiators can instantly see any target reconfiguration in a PnP-like manner) + - - -
Bidirectional Commands + + - - Bidirectional Commands + + - +
Extended CDB (size >16 bytes) + + - - Extended CDB (size >16 bytes) + + - +
Descriptor sense support + + - - + -
Safe RESERVE/RELEASE implementation according to -SCSI requirements 12 Safe Safe Safe from +SCSI requirements 10 Safe Safe Safe from v1.4.18 Not safe
Safe implementation of Task Management commands -13 Safe Not safe Not safe LUN RESET - safe. +11 Safe Not safe Not safe LUN RESET - safe. Other TM commands not implemented.
Safe Support for SCSI task attributes, including ORDERED commands + + -,
data corruption possible - - 14		 -,
data + + 12		 -,
data corruption possible - - 14
Persistent (SCSI-3) Reservations @@ -188,8 +186,11 @@ ORDERED commands + + -,
data Through Power Loss Persistent Reservation data		 Durable Not supported - Not durable
ALUA - - - +/- - 22ALUA +/- (Implicit + only) + 20 + - - +/- + 20
Failover Clustering + + + +
Configuration tool with ability to automatically -apply changes in the config file on fly without any restarts scstadmin - - - scstadmin - - rtsadmin?
SCSI MIBs - - - +- - 15
scsta iSCSI + + + +
QLogic (Fibre Channel) + - - Preliminary - (just added) QLogic (Fibre Channel) + - - Preliminary
Emulex (Fibre Channel and FCoE) + - - -
SRP + - - - SRP + - - Preliminary
iSER - + - 3 - - - iSER - + - -
Marvell (SAS) Beta - - - scsta (not completed) - - -
IBM pSeries Virtual SCSI + + - - IBM pSeries Virtual SCSI + + - Preliminary
Local access to emulated backstorage devices -9 scst_local - - tcm_loop scst_local - - tcm_loop
Supported backstorage @@ -302,35 +300,33 @@ apply changes in the config file on fly without any restarts scsta
SCSI pass-through - 16 + Single + 14 + Single initiator only, not - enforced, limited - functionality for tapes - - 17 + enforced + 15 - Single initiator only, not enforced, limited functionality for tapes - 17
Zero-copy data read/write to/from backstorage BLOCKIO, user space FILEIO in O_DIRECT mode, pass-through - 18 + 16 - - 8 + 6 BLOCKIO BLOCKIO, pass- through
Cache safe11 +Cache safe9 FILEIO Safe Safe only RDWR - backend Safe + (just added) Safe Safe
Cache safe11 -BLOCKIO Safe - Not safe + (just added)Cache safe9 +BLOCKIO Safe - Not safe Safe
4k sectors support in pass-through mode + - - ? - + - - - Experimental - -
Thin provisioning support +
 - - + (just added) Thin provisioning support +
 - - +
- Experimental -
Zero-copy data send/receive Send only - 19 + 17 In some cases, send only - 8 + 6 Send only Send only
+ -
Safe implementation of Task Management commands -13 Safe Not safe Not safe ABORT TASK - not safe, +11 Safe Not safe Not safe ABORT TASK - not safe, LUN RESET - safe, other TM commands not implemented.
Safe implementation of connections and sessions -reinstatement 20 Safe Not safe Not safe Not safe Safe Not safe Not safe Not safe
Usage of hardware instructions for digest -calculations, if available + - - + (just added) + - - +
Each connection multithreaded digest calculation + - - -
Safe restart 21 +Safe restart 19 Safe ? Not safe before v1.4.18. After - probably safe. ?
iSCSI MIBs - - - +- - 15
Local access target
Bidirectional support + - - - Bidirectional support + - - +
Support for AENs (initiators can instantly see any @@ -466,54 +462,43 @@ target reconfiguration in a PnP-like manner) + - 2. All iSCSI management implemented in user space and actual data transfers in kernel space without user space involved.

-

3. ISER target driver has long known (since Feb 2008) data corruption problem, which localization hasn't been - determined yet and might be in the STGT core. See - here, - here and - here.

- -

4. The result "in average" is listed. One target can be better somewhere, another one somewhere else. Although manual tuning of target and +

3. The result "in average" is listed. One target can be better somewhere, another one somewhere else. Although manual tuning of target and system parameters tends the restore the difference listed in the comparison. You can find example measurements here, here and here.

-

5. All SCST and its drivers' kernel patches supposed to be applied and SCST with the drivers built in the release or performance build. +

4. All SCST and its drivers' kernel patches supposed to be applied and SCST with the drivers built in the release or performance build. Without the kernel patches SCST performance will be at "****+" level, except for the case, when user space backstorage handler used with iSCSI-SCST iSCSI target driver, where performance will be at "***+" level.

-

6. There is no performance data for LIO, which allow to make a direct comparison with other targets. - The conclusion was made based on source code study. LIO should have performance on the IET level or less, - because of more processing overhead. It might be much less for small block sizes. Also the single I/O thread per-device - approach LIO has is not optimal in many cases.

- -

7. In SCST data are always passed in zero-copy manner between target and backend drivers without need for any +

5. In SCST data are always passed in zero-copy manner between target and backend drivers without need for any additional kernel patches, except in case, when local access (scst_local) used with user space backend.

-

8. Some zero-copy functionality isn't available from user space, sometimes fundamentally. +

6. Some zero-copy functionality isn't available from user space, sometimes fundamentally. For instance, zero-copy FILEIO with page cache or zero-copy send to a socket. Also STGT can't use splice() for in-kernel target drivers, because it has memory management in user space. To use splice() with socket-based user space target drivers STGT would need a deep redesign of internal interactions between target drivers, core and backend handlers. But in some cases STGT can use zero-copy sendfile().

-

9. Local access to emulated backstorage devices" means that you can access emulated by a SCSI target devices +

7. "Local access to emulated backstorage devices" means that you can access emulated by a SCSI target devices locally on the target host. For instance, you can mount your ISO image from emulated by the target CDROM device locally on the target host.

-

10. "Advanced devices access control" means that different initiators can see different sets +

8. "Advanced devices access control" means that different initiators can see different sets of devices from the same target. This feature is required for hardware targets, which don't have ability to create virtual targets.

-

11. "Cache safe" means that cache synchronization commands (SYNCHRONIZE_CACHE and FUA attribute) from initiators perform +

9. "Cache safe" means that cache synchronization commands (SYNCHRONIZE_CACHE and FUA attribute) from initiators perform what they expected to perform, i.e. push all the requested blocks from all caches, including devices' caches, to non-volatile media.

-

12. SCSI requires that if an initiator clears reservation held by another initiator, the reservation holder must be notified +

10. SCSI requires that if an initiator clears reservation held by another initiator, the reservation holder must be notified about the reservation clearance. Otherwise, several initiators can at the same time change supposed to be protected by the reservation data, which can corrupt them. This is what was called "Russian roulette with your data" on the VMware community forum by someone working for VMware. But, sure, it can affect not only VMware, but also any other cluster implementation, relying on this functionality.

-

13. After a task management command completed and before the corresponding response was sent to the initiator, who sent that task management +

11. After a task management command completed and before the corresponding response was sent to the initiator, who sent that task management command, all the affected SCSI commands must get into a state, where they can't affect following after the tasks management response commands from this initiator. This is the safe implementation. The unsafe implementation only marks all the affected @@ -523,44 +508,43 @@ target reconfiguration in a PnP-like manner)

 + - -

14. Both IET and LIO report in INQUIRY command response support for full task management model. But they process ORDERED +

12. Both IET and LIO report in INQUIRY command response support for full task management model. But they process ORDERED commands the same way as SIMPLE commands, i.e. allow free reorder of them before they get executed. That violates SCSI standard and can lead to a data corruption to any application relying on commands order provided by ORDERED attribute.

-

15. LIO exports the information needed for an RFC 4455 implementation, but requires additional RFC 4455 implementing module. +

13. LIO exports the information needed for an RFC 4455 implementation, but requires additional RFC 4455 implementing module. At the moment, there is no open source implementation of such module.

-

16. SCSI pass-through mode allows to export your local SCSI-capable device. For instance with it you can share your parallel +

14. SCSI pass-through mode allows to export your local SCSI-capable device. For instance with it you can share your parallel SCSI tape or SATA DVD-RW device to your iSCSI network.

-

17. STGT and LIO don't emulate all the necessary SCSI host functionality to allow to share SCSI devices +

15. STGT and LIO don't emulate all the necessary SCSI host functionality to allow to share SCSI devices in pass-through mode to several initiators, although LIO has some necessary processing, but not all. They can only pass SCSI commands from initiators to SCSI devices and responses back. This is safe only with a single initiator. This limitation isn't enforced anyhow and both STGT and LIO don't issue any warning about it, so an user will not be notified about this limitation and can quietly corrupt his/her data. You can find more technical information about it here. - Also neither STGT, nor LIO in pass-through mode do the necessary sense processing for tape devices to - correctly return residual information, so tapes can used with them with limited functionality.

+ Also LIO in pass-through mode doesn't do necessary sense processing for tape devices to + correctly return residual information, so tapes can used with it with limited functionality.

-

18. You can find a proposal how to implement zero-copy FILEIO in SCST on the +

16. You can find a proposal how to implement zero-copy FILEIO in SCST on the Contributing page.

-

19. Doesn't need any kernel patch, except in the case, when used with user space backend.

+

17. Doesn't need any kernel patch, except in the case, when used with user space backend.

-

20. Connections and sessions reinstatement is, basically, a kind of Task Management command, because it implies commands aborting. +

18. Connections and sessions reinstatement is, basically, a kind of Task Management command, because it implies commands aborting. So, similarly to the safe task management above, a safe implementation of connections and sessions reinstatement must not accept SCSI commands from new connection/session until all the SCSI commands in being reinstated connection/session get into a state, where they can't affect new commands.

-

21. "Safe restart" means that after the iSCSI target restart, all the connected initiators will seamlessly restore all existing before +

19. "Safe restart" means that after the iSCSI target restart, all the connected initiators will seamlessly restore all existing before the restart connections. "Not safe" means that, most likely, the connected initiators will fail to restore existing connections with some errors. However, your iSCSI initiator also should be able to handle the safe restart. For instance, old (pre-CentOS/RHEL 5) open-iscsi has problems in this area. But the latest versions do it pretty well.

-

22. All ALUA states - transitioning implemented as empty placeholders, which means this implementation can't be used to build ALUA-based - clusters without additional code.

+

20. Generic implementation, i.e. not coupled to any particular cluster implementation, which means it is needed additional effort + to used with each particular cluster setup.

diff --git a/www/downloads.html b/www/downloads.html index 4f29958b1..c2e9c2005 100644 --- a/www/downloads.html +++ b/www/downloads.html @@ -36,8 +36,10 @@

SCST Downloads

-

The latest stable released version of SCST core is 2.0.0.1. It requires Linux kernel 2.6.18 or higher. - More detail information you could find in its README file.

+

The latest stable released version of SCST core is 2.0.0.1. The latest updates for it + you can find it in the SVN branch 2.0.0.x.

+ +

The latest stable pre release version is 2.1-rc1. You can find it in the SVN branch 2.1.0.x.

You can also download prebuilt SCST modules for Scientific Linux CERN 5 (RHEL5-based), diff --git a/www/index.html b/www/index.html index 4946ae8f9..16bf3b9d8 100644 --- a/www/index.html +++ b/www/index.html @@ -151,6 +151,7 @@

Gentoo HOWTO For iSCSI-SCST

Alpine Linux HOWTO

HOWTO For QLogic Target Driver

+

Ubuntu/Debian HOWTO For QLogic Target Driver

HOWTO For Emulex lpfc Target Driver

SCST SGV Cache Description

Articles

diff --git a/www/mc_s.html b/www/mc_s.html index aa96cabaf..d669196ed 100644 --- a/www/mc_s.html +++ b/www/mc_s.html @@ -37,6 +37,7 @@

Comparison

diff --git a/www/scstvslio.html b/www/scstvslio.html new file mode 100644 index 000000000..4df7beece --- /dev/null +++ b/www/scstvslio.html @@ -0,0 +1,119 @@ + + + + + + + +SCST vs LIO/TCM + + + + +
+ + + + + +
+ + +
+

SCST vs LIO/TCM

+

LIO, from recently being renamed to TCM, is another independent from SCST implementation + of SCSI target framework for Linux. It's started as PyX iSCSI target and then was + accommodated to other transports. But it's still in many kinds iSCSI-oriented. + You can find an example when people are not happy with it + here.

+ +

LIO maintainer, Nicholas Bellinger, is very good in building personal relationships and promoting LIO, + although often using misleading half, less-then-half and simply deceitful statements + about LIO current state, capabilities and future directions as well as about its competitor, SCST. + For instance, he setup LIO targets comparison page with obviously wrong statements about SCST, like + that it isn't fully zero copy or it isn't a generic target engine (while LIO, of course, is fully + zero-copy and fully generic target engine). Any + attempts + to correct it were simply ignored.

+ +

With those tricks Nicholas Bellinger was capable to attract key Linux kernel developers, and + they suddenly changed their opinion about Linux SCSI target subsystem in the opposite direction. + They previously asserted that + in-kernel SCSI target is the wrong direction, SCSI target must be in the user space, so + STGT is what everybody needed. Now their opinion is that SCSI target driver should be in the kernel space + and the only target good for them is LIO, doesn't matter that:

+ +
    +
  1. SCST is a lot more mature and advanced
    2. + +
  2. SCST from the beginning is a generic SCSI target
    3. + +
  3. SCST has a lot more features
    4. + +
  4. SCST has better performance
    5. + +
  5. SCST has a lot more users
    6. + +
  6. SCST has much bigger community
    7. + +
+ +

So, rejecting base principles of the Linux kernel community that the best code should win, the worst + code was chosen.

+ +

You can find more background behind choosing LIO as the mainline kernel SCSI target + subsystem if you read this thread + as well as searching for targets related topics in Linux kernel and Linux SCSI mailing lists.

+ +

Particularly notable is that James Bottomley from the beginning was telling that SCST + can't be merged in the mainline kernel, because it doesn't offer a drop in replacement for STGT + to avoid having 2 target infrastructures in the kernel at the same time. But, since LIO can't + offer user space backend drivers and doesn't have ibmvstgt driver analog, for LIO the drop in replacement wasn't + a requirement, so 2.6.38+ kernels successfully have both STGT and LIO.

+
+
+
+ + + + + + + + + + diff --git a/www/scstvsstgt.html b/www/scstvsstgt.html index a7c80f29e..7b2a91499 100644 --- a/www/scstvsstgt.html +++ b/www/scstvsstgt.html @@ -37,6 +37,7 @@

Comparison

@@ -70,10 +71,8 @@ -

Also don't be deceived by the fact that some (small) part of STGT was accepted into the kernel.
- It doesn't mean that STGT has the "kernel quality". STGT as a whole similarly to any other - out-of-kernel-tree project lives on its own, hence has its own quality level, which isn't necessary better, than the - quality level of SCST.

+

Time has proved that STGT is too weak to satisfy modern storage requirements. Now it is obsolete and + soon going to be removed from the mainline kernel.