6.7.2 Slow write speeds with cache enable

[Aviv]

Hi!
Im getting about 55mbs when using SSD as a cache when transferring from my linux machine to unraid.

Writing directly to the ssd using "unassigned plugin" yield about 70-80mbs only.

both computers are connected with 1gb connection.

The unraid build is old hardware:
I5-650 cpu, 8gb ddr3 ram. 
IronWolf pro 4tb X 2 + 1 Sandisk 250gb ssd.

Any tips regarding how to debug it? (im new!)

[trurl]

Go to Tools - Diagnostics and attach the complete diagnostics zip file to your NEXT post.

[Aviv]

35 minutes ago, trurl said:

Go to Tools - Diagnostics and attach the complete diagnostics zip file to your NEXT post.

How do I hide the encryption key from the diagnostics report?

[trurl]

10 minutes ago, Aviv said:

How do I hide the encryption key from the diagnostics report?

I've never heard of the encryption key appearing in the diagnostics. Are you sure it's there?

[JonathanM]

And also, does the speed improve if you are not using encryption?

[bonienl]

1 hour ago, Aviv said:

How do I hide the encryption key from the diagnostics report?

The encryption key is NEVER part of diagnostics

[Aviv]

I believe i got it all wrong..

The transfer speed show from my linux machine is in MiB's, eg I believe that 56MiB's is about 400Mbps. so, my bad. all good. right?

Edited November 4, 2019 by Aviv

[itimpi]

31 minutes ago, Aviv said:

I believe i got it all wrong..

The transfer speed show from my linux machine is in Mib's, eg I believe that 56Mib's is about 400Mbps. so, my bad. all good. right?

Normally when quoting speeds it is conventional to use a capital 'B' when you mean bytes and a lower case 'b' when you mean bits.  That helps with deciding what units one is talking about.

[Aviv]

Sorry, im new at this:) Updated my post. im getting 56MIB/s. I think its ok. as this is the speed of a sata ssd.

[itimpi]

8 minutes ago, Aviv said:

I think its ok. as this is the speed of a sata ssd.

That sounds very slow for a SSD.   I would expect it to be more like 560 MB/s.

[Aviv]

56MiB/s is about 469.8 Mbps. my ssd model supports Sequential Write (up to) 350MB/s (SanDisk_SSD_PLUS_240GB).

So i think im good. but still not sure i get the numbers right.

 

 

[testdasi]

2 hours ago, Aviv said:

56MiB/s is about 469.8 Mbps. my ssd model supports Sequential Write (up to) 350MB/s (SanDisk_SSD_PLUS_240GB).

So i think im good. but still not sure i get the numbers right.

 

 

 

In case you are still confused about the unit.

• MB/s = megabyte/s = 1 million bytes/s
• MiB/s = Mebibyte/s = 1,048,576 bytes/s

 

56MiB/s can be a reasonable speed if your data is not too sequential in nature.

It would be certainly too slow if you data is highly sequential e.g. a large ISO image.

So it depends.

 

Note though that since you are transferring over gigabit network, your max speed will be limited to 1Gb/s = 125MB/s (8 bits = 1 byte).

So you will never get anywhere close to 350MB/s sequential unless there are multiple simultaneous independently connected clients.