iSCSI FAQ
- What is iSCSI?
iSCSI stands for Internet Small Computer System Interface, an Internet Protocol IP-based storage networking standard for linking data storage facilities.
- What is SPC-3 (SCSI-3)? Persistent Reserve?
SCSI Primary Commands – 3(SPC-3) contains the third-generation definition of the basic commands for all SCSI devices. Please refer to http://www.t10.org/ for more details.
Persistent Reserve refers to a set of Small Computer Systems Interface-3 (SCSI-3) standard commands and command options which provide SCSI initiators with the ability to establish, preempt, query, and reset a reservation policy with a specified target device. Many systems (Windows 2008 failover cluster, VMware etc.) need the commands to be supported in order to work properly.
- What do I need to use iSCSI?
- You will need iSCSI initiators, either software initiators or HBA (Host Bus Adapter). For Windows operating system, you can download Microsoft iSCSI Software initiator from Microsoft’s web site (http://www.microsoft.com/downloads/en/default.aspx).
Note: Windows 2008 and Windows Vista both offer a built-in iSCSI initiator. You can find them in the Control Panel and Administrative Tools respectively.
- iSCSI target: QNAP Turbo NAS all support built-in iSCSI service. You can use the Turbo NAS as an iSCSI target.
- What is an iSCSI initiator and what is an iSCSI target?
Initiator
An initiator functions as an iSCSI client. An initiator typically serves the same purpose to a computer as a SCSI bus adapter would, except that instead of physically cabling SCSI devices (like hard drives and tape changers), an iSCSI initiator sends SCSI commands over an IP network (quoted from Wiki).
Target
iSCSI specification refers to a storage resource located on an iSCSI server (more generally, one of potentially many instances of iSCSI storage nodes running on that server) as a target. An iSCSI target usually represents hard disk storage that works over the IP or Ethernet networks (quoted from Wiki).
- Do QNAP iSCSI products support MPIO, MC/S?
- QNAP Turbo NAS product line supports (since firmware 3.2.0 in x86-based and firmware 3.3.0 in ARM-based) MC/S.
- QNAP NAS support MPIO (since firmware 3.2.0 in x86-based and firmware 3.3.0 in ARM-based) to co-operate with Windows 2008 only.
- What do Thin-Provisioning and Instant Allocation mean when setting up a LUN?
Thin-Provisioning is a method of optimizing the efficiency with which the available space is utilized in the NAS. If you select Thin-Provisioning when building an iSCSI LUN, the disk space can be more flexibly used. However, it is not guaranteed that the iSCSI Target has enough disk space as specified.
Compared with Thin-Provisioning, Instant Allocation allocates disk space beyond current needs.
- How many LUNs and Targets can be created on QNAP NAS?
Different models have different limitations. For example, TS-809 Pro supports 256 iSCSI LUNs and 256 iSCSI Targets at maximum. For more details, please refer to the product comparison table on our web site.
- Can I expand the disk capacity of my NAS if it is almost full?
Yes, you may increase the physical disk capacity by “Online RAID Capacity Expansion”
- Can I expand the LUN size if it is almost full?
Yes, since firmware 3.X.X in x86-based and firmware 3.X.X in ARM-based.
- What is the maximum size for each LUN?
If you create an iSCSI LUN with Thin-Provisioning, the maximum size can be 32768GB. If you use Instant Allocation, the maximum size is equal to remain capacity of the selected disk volume.
- Do QNAP NAS products support LUN masking or ACL?
Yes, QNAP Turbo NAS all support LUN masking (since firmware 3.2.0 in x86-based and firmware 3.3.0 in ARM-based). You can set up LUN masking or ACL by each initiator. In other words, each initiator can have different access right to each LUN.
- Can a LUN be mapped to several different iSCSI Targets?
No, an iSCSI LUN can be mapped to only one iSCSI Target.
- Can an iSCSI LUN be accessed by multiple iSCSI initiators?
It is possible to access a single iSCSI LUN ONLY IF using cluster aware file system such as GFS or OCFS2 or any other cluster mechanism such as Windows 2008 Failover Cluster. Otherwise, the LUN file system will be corrupted.
- Why can’t I see an over-2-TB iSCSI LUN in my Windows OS?
This is a known issue with Microsoft’s initiator that it can only handle 2TB or less. You can use the GUID Partition Table (GPT) to solve this problem. For more details, please refer to the Microsoft GPT FAQ.
- What actions of the NAS will lead to iSCSI disconnection?
The following actions will lead to iSCSI disconnection:
- Modify the network settings.
- All actions on the Volume Management page.
- SMART scan.
- Modify all iSCSI related settings.
- Format any internal disk.
- Perform check disk function to a disk with iSCSI LUNs.
- Hot plug out a disk.
- What is the IOPS of QNAP iSCSI service?
|
Sequential Write |
Sequential Read |
Random Write |
Random Read |
|
| TS-809 Pro |
22541 |
35771 |
||
| TS-809U-RP |
21553 |
34416 |
||
| TS-259 Pro |
11885 |
15660 |
||
| TS-459 Pro |
11475 |
15436 |
||
| TS-459U-RP/SP |
12334 |
15882 |
||
| TS-559 Pro | ||||
| TS-659 Pro |
12112 |
15560 |
||
| TS-859 Pro |
12341 |
15442 |
||
| TS-859U-RP |
11985 |
15236 |
||
| TS-259 Pro+ | ||||
| TS-459 Pro+ | ||||
| TS-559 Pro+ | ||||
| TS-659 Pro+ | ||||
| TS-859 Pro+ | ||||
| TS-239 Pro II |
8187 |
13458 |
||
| TS-439 Pro II |
8283 |
14016 |
||
| TS-439U-RP |
6855 |
11895 |
||
Test environment:
|
Test Client |
|
| Processor | Intel Core2 Quad Q8300 2.5GHz |
| Memory | 4GB DDRII 800 |
| Main board | ACER EG31M |
| HDD | WD1500HLFS 150G/10000 RPM |
| Volume | Single |
| Network Adapter | Intel Dual Port Server 82571 |
| OS | Windows 7 Enterprise 32 Bits |
| Test File | 5GB File*1 |
|
NAS Configurations |
|
| File System | EXT4(with write cache enable) |
| Network Mode | Fixed IP, Standalone |
| Connection | PC connected to NAS directly |
- What is the iSCSI performance of QNAP iSCSI service?
|
Sequential Write(MB/s) |
Sequential Read(MB/s) |
|
| TS-809 Pro |
100.3 |
81.3 |
| TS-809U-RP |
99.7 |
81.2 |
| TS-259 Pro |
79.9 |
82.1 |
| TS-459 Pro |
80.5 |
79.1 |
| TS-459U-RP/SP |
82.5 |
80.0 |
| TS-559 Pro | ||
| TS-659 Pro |
81.4 |
81.7 |
| TS-859 Pro |
81.3 |
79.0 |
| TS-859U-RP |
81.5 |
80.2 |
| TS-259 Pro+ | ||
| TS-459 Pro+ | ||
| TS-559 Pro+ | ||
| TS-659 Pro+ | ||
| TS-859 Pro+ | ||
| TS-239 Pro II |
75.4 |
72.6 |
| TS-439 Pro II |
73.8 |
72.9 |
| TS-439U-RP |
70.9 |
67.6 |
- How to backup iSCSI LUN?
- iSCSI initiator compatibility list.
Test Firmware: 3.2.5 (0408)
| Initiator /iSNS Software | Support OS | Result | Bugs No. and Description |
| Microsoft iSCSI Initiator 2.08 | Windows XP | Chap/Mutual Chap | PASS |
| CRC/Head Digest | PASS | ||
| iSNS | PASS | ||
| Microsoft iSCSI Initiator 2.08 | Windows Vista | Chap/Mutual Chap | PASS |
| CRC/Head Digest | PASS | ||
| iSNS | PASS | ||
| Microsoft iSCSI Initiator
2.08 |
Windows 2003 | Chap/Mutual Chap | PASS |
| CRC/Head Digest | PASS | ||
| iSNS | PASS | ||
| MPIO | PASS | ||
| MCs | PASS | ||
| Microsoft iSCSI Initiator 內建 | Windows 2008 | Chap/Mutual Chap | PASS |
| CRC/Head Digest | PASS | ||
| iSNS | PASS | ||
| MPIO | PASS | ||
| MC/S | PASS | ||
| Failover Cluster | PASS | ||
| Microsoft iSCSI Initiator
內建 |
Windows 2008 R2 /Windows 7 | Chap/Mutual Chap | PASS |
| CRC/Head Digest | PASS | ||
| iSNS | PASS | ||
| MPIO | PASS | ||
| MC/S | PASS | ||
| Failover Cluster | PASS | ||
| VMware ESX Initiator | VMware ESX4.0 | Chap/Mutual Chap | PASS |
| CRC/Head Digest | PASS | ||
| Vmotion | PASS | ||
| SP failover/NIC failover | Pending | ||
| LUN Reset/Release | Pending | ||
| Xtend SAN version 3.25 | Mac OS 10.6 | Chap/Mutual Chap | PASS |
| CRC/Head Digest | PASS | ||
| globalSAN version 4.0 (Build 204) 正式版 | Mac OS 10.6 | Chap/Mutual Chap | FAIL Using Mutual CHAP cause mac O S crashed (known issue) |
| CRC/Head Digest | PASS | ||
| iscsi-initiator-utils-6.2.0.868-0.18.el5 | Red hat 5 | Chap/Mutual Chap | PASS |
VMware Related FAQ
- I can connect to QNAP iSCSI service in VMware vCenter but cannot find any LUN. What should I do?
This usually happens when you have wrong network configuration of VMkernel port in vCenter. Try to ping your IP of VMkernel port from QNAP NAS to make sure the connection between the VMkernel port and Turbo NAS.
Windows 2008 FAQ
- I found iSCSI connection drop-out log in the Windows 2008 system log. What should I do?
iSCSI is block level protocol and it is sensitive with the quality of network connection. All elements on the packet transmission path are important. Here are several hints and will assist you to improve the connection quality.
Turbo NAS:
- Update the firmware to latest version.
- Try not to use jumbo frame in Network configuration. Set the MTU to 1500 instead of 9000.
- DisableNetwork Port Trunking
- Use specific network speed instead of auto-negotiation in TCP/IP setting.
- Try to assign a specific NIC for iSCSI service.
Windows OS:
- Update the Windows OS and patch the Windows Hot Fix.
- Use the latest MS initiator.
- Use the latest driver of your server NIC.
- Disable the jumbo frame setting of your server NIC in Advanced properties.
- Enable flow control of your server NIC in Advanced properties.
- Increasing the Receive buffers (descriptors) on your server NIC(s) in Advanced properties
- Adjust Microsoft initiator Driver time settings in the registry:
Key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E97B-E325-11CE-BFC1-08002BE10318}\<Instance Number>\Parameters
Where the <Instance Number> is the MS software initiator index. Just browse the DriverDesc value under it to see if it is “MicrosoftiSCSI initiator”.
- MaxRequestHoldTime
Default is 60, please change to 600 in decimal format (00000258 in hexadecimal).
- SRBTimeoutDelta
Default is 15, please change to 180 in decimal format (000000B4 in hexadecimal).
Restart the Window host to active these new settings
- Adjust Microsoft Disk Driver Timeout settings in the registry:
Key: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Disk
- TimeOutValue
Edit or add the TimeOutValue entry to set it to 180 in decimal format (000000B4 in hexadecimal). To edit the value for the TimeOutValue entry if it already exists, double-click the entry, enter the new value, and click OK. To add the TimeOutValue entry if it does not yet exist, right-click anywhere in the list of values, and click New > DWORD value. Name the new value TimeOutValue in decimal, and then double-click it to edit the setting.
Restart the Window host to active these new settings.
Switch:
- Use VLAN to separate iSCSI protocol with other protocol.
- Enable flow control on the switch.
- Enable or disable jumbo frame settings according to the Jumbo Frames configurations on the Turbo NAS.
- Set more buffer for the port which is used by Turbo NAS.
- Use specific network connection speed instead of auto-negotiation.
ISCSI Hakkında Sık Sorulan Sorular & CevaplarFAQ About ISCSI,
