Greetings 

So I now have a dell t420 with the perc raid controler and 8 drives and i entend to replace my ryzen 7 unraid server with it

 

With the perc you at least must do raid 0 virtual drives  that will be presented to unraid

 

I can't decide between 2 options

 

I/ Make 4 raid 0 virtual drives with the perc and then have an array of 3 drives and one parity, unraid will then deal with data loss prevention

II/ Make some raid 5 or 10 with the perc and an array with no parity and have the raid controler  deal with data loss prevention.

 

I can't decide and don't know what will be best 

so if anyone have advice??

 

thank you

best regards 

Edited February 5, 20206 yr by salora

Well I can say I made a lots of trials and I tried both solutions since, and what makes me perplex is the low writing rates on unraid and there are a lot of topics on that!

drives are all sata 3 

 

so with a normal array set up (drives and parity) writing speed don't go above 20mb/s to 40mb/s ish with turbo cacha and other solutions found (Disk Cache Settings..) on other topics

reading writes are ok

 

with the raid 5 on the perc and one big drive presented to unraid, no parity its better, writing speed up to 70mb/s.

 

BUT with a the raid 5 presented to a windows Server OS well, writing speed is up to 120Mb/s , saturating a gigabit ethernet link, with the same drives and perc configuration

with the sames drives on an  Xpenology setup with a poor asrock j1900 motherboard writing speed is also up to 120Mb/s , saturating a gigabit ethernet link

So I don't understand Unraid is basically a NAS OS for a start , why is the writing speed so low no matter what??

1 hour ago, salora said:

so with a normal array set up (drives and parity) writing speed don't go above 20mb/s to 40mb/s

It can perform much better, some people really got slow problem, but I can't reproduce even with a J1800 system. ( you must ensure always one write session is active and enable reconstruction write mode )

 

I don't think RAID disks by RAID card is a good solution, it will lost disk health monitoring and flexibility of disk migrating. For the need of breaking thr single disk performance, you can RAID it by cache pool or UD.

 

 

Edited April 28, 20206 yr by Benson

With turbo write you should be able to write to the array as fast as your slowest device, Unraid is not made for performance but it can be fast as long as the hardware used allows it, e.g.:

 

 

This is writing directly to the array, not cache, but all array members are a couple of disks in raid0.

2 hours ago, Benson said:

It can perform much better, some people really got slow problem, but I can't reproduce even with a J1800 system. ( you must ensure always one write session is active and enable reconstruction write mode )

 

I don't think RAID disks by RAID card is a good solution, it will lost disk health monitoring and flexibility of disk migrating. For the need of breaking thr single disk performance, you can RAID it by cache pool or UD.

 

 

reconstruction write mode is activate and no better performances i tried

 

health monitoring is done through dell IDRAC so not an issue at all

2 hours ago, johnnie.black said:

With turbo write you should be able to write to the array as fast as your slowest device, Unraid is not made for performance but it can be fast as long as the hardware used allows it, e.g.:

 

 

This is writing directly to the array, not cache, but all array members are a couple of disks in raid0.

well okay I get your point

I have these speed too while it's writing to RAM ( the dirty cache setting) but when it's filled the writing speed drop (like many others from what i've read)

my "slowest disk"  can perform at at least 120Mb/s on a raid array with windows or xpenology and not unraid ! that I don't understand

I tried the  DiskSpeed app to analyse and the average speed on each disk is much higher than that so I can't get why disks able to more than 150mb/s get down to 40 when putted in an array.

I get Unraid is not made for top perfomance but still ...

Edited April 28, 20206 yr by salora
additon

14 minutes ago, salora said:

I have these speed too while it's writing to RAM ( the dirty cache setting) but when it's filled the writing speed drop (like many others from what i've read)

Yes, but I wasn't writing to RAM, on the example above only the first few GB are cached to RAM as seen in the transfer graph, here's an example of a much larger transfer:

 

 

My point was that Unraid can be fast, the speed you're experiencing suggests some issue, either hardware or config.

 

And for a more normal example, this is another Unraid server with standard disks as devices, in fact they are SMR, though that's usually fine with Unraid:

 

3 minutes ago, johnnie.black said:

Yes, but I wasn't writing to RAM, on the example above only the first few GB are cached to RAM as seen in the transfer graph, here's an example of a much larger transfer:

 

 

My point was that Unraid can be fast, the speed you're experiencing suggests some issue, either hardware or config.

 

config maybe, hardware it can't be otherwise i'll had the same issues with other OS

Just now, salora said:

hardware it can't

I'm not necessarily saying hardware is bad, might just not be good with Unraid, perc h710 is a good example of that, not sure how good that driver is for linux, it's certainly not a recommended controller, LSI based HBAs are recommended.

5 hours ago, salora said:

with turbo

I assumed you were talking about this thread which explains how parity writes impact write speed. Here it is in case you haven't seen it:

 

 

1 minute ago, johnnie.black said:

I'm not necessarily saying hardware is bad, might just not be good with Unraid, perc h710 is a good example of that, not sure how good that driver is for linux, it's certainly not a recommended controller, LSI based HBAs are recommended.

Yes I know it's not ideal, i'm trying to get hand on a h310 to flash on it mode

I said i've done a lot of trials , there is a sata port directly on the motherboard I tried it an even that way with drives directly shown to unraid it's bad with or without turbo mode, reconstruct mode..

 

other than the perc there is dual xeon with 16 cores (and HT) , 128 Gb ECC ram so it's not a low end rig

So mooved everything to windows server and hyper-v with a virtual machine running the file server and smb shares

the drives are in raid 5 on the perc h710 and I've more thant 400mb/s transfer rate so maybe a dell server is not made to run unraid I don't know

1 hour ago, salora said:

so maybe a dell server is not made to run unraid

Like mentioned already the raid controller is likely the main issue, HBAs or just regular SATA ports are recommended for Unraid.

2 hours ago, salora said:

drives are in raid 5 on the perc h710 and I've more thant 400mb/s transfer rate

Unraid is NOT RAID, you will never get RAID5 speeds on Unraid. Unraid has other advantages.

11 hours ago, johnnie.black said:

Like mentioned already the raid controller is likely the main issue, HBAs or just regular SATA ports are recommended for Unraid.

Indeed but like said already I tried with the embedded sata port of the motherboard with no better luck

11 hours ago, trurl said:

Unraid is NOT RAID, you will never get RAID5 speeds on Unraid. Unraid has other advantages.

I know i've been using unraid for 4 years

but still from 400mb/s to less thant 40 ! that is huge drop down

12 minutes ago, salora said:

with the embedded sata port of the motherboard with no better luck

If it's just one port and the other drives are still on the RAID controller it won't make any difference.

2 hours ago, johnnie.black said:

If it's just one port and the other drives are still on the RAID controller it won't make any difference.

No sir I beg to disagree

It's an embedded sas port that can handle 6 sata drives

So of course all drives are connected to the main board and seen by unraid and not the raid controller

 

 

34 minutes ago, salora said:

It's an embedded sas port that can handle 6 sata drives

But is that a SAS or SATA controller? What controller and driver is in use? I never had any Dell servers so no idea what's there, I was talking about regular AHCI SATA ports, mostly the ones from an AHCI enable Intel controller, anything other than that may or may not have the similar issues.

it is a standard AHCI SATA controler, but the connector is a mini sas port so you need the right cable to attach the sata drives 

like that for example

 

https://www.amazon.fr/CableDeconn-SFF-8087-SFF-8482-Connecteurs-alimentation/dp/B010CMW6S4/ref=sr_1_1?__mk_fr_FR=ÅMÅŽÕÑ&keywords=CABLEDECONN+Mini+SAS+36+SFF-8087+to+(4)+SFF-8482+Connectors+with+SATA+Power+1m&qid=1585484930&sr=8-1

12 minutes ago, salora said:

it is a standard AHCI SATA controler, but the connector is a mini sas port so you need the right cable to attach the sata drives 

like that for example

Them it should perform as expected, i.e., as fast as your slowest disk with turbo write enable.

 

You can use this to check the speed of your devices and if the writing speed (using the SATA ports and turbo write) is far from the slowest disk post the diagnostics grabbed during a transfer.