iSCSI performance unacceptable

[Gr-R]

Try this:

1. From the console, press CTRL+ALT+W,
2. Select Tuning options -> iSCSI daemon options -> Target options,
3. Select the target in question,
4. change the MaxRecvDataSegmentLength and MaxXmitDataSegmentLength values to the maximal required data size

(check w/ the initiators to match).

maxRecvDataSegmentLen=262144
MaxBurstLength=16776192
Maxxmitdatasegment=262144
FirstBurstLength=65536
DataDigest=None
maxoutstandingr2t=8
InitialR2T=No
ImmediateData=Yes
headerDigest=None
Wthreads=8

[sebus]

These settings do make the speed jump to a more acceptable 42Mb/s on write

sebus

[Gr-R]

At this point, without hardware raid, your at about the top for tuning your setup.

With hardware raid, there are more things to tune for speeds.

One other thing to use is block I/O and WT on the targets, if not already.

[sebus]

For a D2D2T backup it will have to do, no space to fit RAID card

Why these options are not default then?

sebus

[Gr-R]

Since the daemons that run the connections are open source, and we don't know with certainty what each system may involve, or hardware used, we stay on the defaults to start with.
But for backups, that's not to bad really.

[To-M]

Make sure the LUN has the Write Back enabled. Also check the test.log and tell me what the hdparm are for the reads - cut an past on your post.

Also SeanLeyne is correct that those drives are slow "Seagate 5900 RPM" with the seek times at that rate dont expect great performance values especially again a RAID controller with faster drives again slow drives with no RAID controller to tune with the Write Cache that is available with the RAID controller.

[sebus]

Just for the fun I build another unit with exactly the same spec & this time used FreeNAS FreeNAS-8.0-RELEASE-amd64.Full_Install

Default install with same tweaks as per Gr-R recommendation

Both servers connected to the same switch via identical Cat6 cable

So all in all the hardware is a TWIN, just the OS is different

Then I used Copy Handler 1.32 to copy same 1.59Gb of data from internal HD to both units:

First FreeNAS:

45 sec, avg 36.26 MB/s

Then DSS:

4 min 16 sec, 6.37 MB/s

Surely not what one should/could expect?


And that is exactly what I see during normal use of the machine.
Open-e ISCSI volume can not be accessed when something is writing to it

With FreeNAS I can read (open large rar) while another process writes to the volume (ie file copy)

sebus

[Al-S]

Try this:

1. From the console, press CTRL+ALT+W,
2. Select Tuning options -> iSCSI daemon options -> Target options,
3. Select the target in question,
4. change the MaxRecvDataSegmentLength and MaxXmitDataSegmentLength values to the maximal required data size

(check w/ the initiators to match).

maxRecvDataSegmentLen=262144
MaxBurstLength=16776192
Maxxmitdatasegment=262144
FirstBurstLength=65536
DataDigest=None
maxoutstandingr2t=8
InitialR2T=No
ImmediateData=Yes
headerDigest=None
Wthreads=8

As an update, please keep in mind when using latest builds of DSS, MaxBurstLength variable cannot be set to 16776192 because such value was only supported in iSCSI Enterprise Target (IETD), additionally With reads variable also works only with (IETD).

Max value in SCST for MaxBurstLength is 1MB, 10485760.

In case when you use MaxBurstLength=16776192 and make the update, scripts during starting the system fix the values to default one (262144).

So you may leave MaxBurstLength variable values as the default value or you may use the max value which is 10485760.

[DIESOFTWARE-RS]

@Al-S

You got a bad Typo there:

Max value in SCST for MaxBurstLength is 1MB, 10485760
.
.
So you may leave MaxBurstLength variable values as the default value or you may use the max value which is 10485760.

should read:

Max value in SCST for MaxBurstLength is 1MB, 1048576
So you may leave MaxBurstLength variable values as the default value or you may use the max value which is 1048576.


Just one "0" to much...

Regards,
Ralph