PowerEdge HDD/SCSI/RAID

[arenault]

Hello everyone,

I am looking into having the following arrangement on a PERC H730:

1x RAID1 volume w/ (2) 960GB 6Gbps SATA drives

1x RAID10 volume w/ (8) 1.8TB 12Gbps SAS drives

Should I expect the whole bus to drop to SATA 6Gbps specs?

Should I have the volumes on separate controllers (i.e. 1 on server, other on DAS) for maximum performance?

Thanks for the input!

[DELL-Daniel My]

Hello

Should I expect the whole bus to drop to SATA 6Gbps specs?

No, the controller negotiates speeds with each drive. You can have drives within the same virtual disk negotiated to different speeds. It does not negotiate all speeds to the lowest common speed within either a virtual disk or across the controller.

https://www.dell.com/perc

Thanks

[arenault]

Is this something that came as a recent evolution in controllers?

I feel that in the past several years, whenever I added SAS drives to an enclosure with PERC H700 and SATA drives, I didn't get the performance boost I expected from SAS.

Maybe the PERC H730 is better at that?

[theflash1932]

A slower interface would slow the entire bus on SCSI - if you mixed SCSI U160/U320 either one or the other would work, none of them would work, or they would all negotiate down to the lowest common speed, depending on the actual controller and generation. I think there may have even been an issue negotiating different speeds with the introduction of SAS/SATA 1.5/3Gbps on early controllers. For the last 10 years or so, most will negotiate with individual drives. At least on Dell systems - I'm sure cheaper and consumer controllers don't do it.

[arenault]

Yes, I remember the issues with older SCSI interfaces.

I'm looking at the 2 configurations below.

Any likely difference in performance?

Environment is VMware. The VM virtual disk containing OS and database will be on SSD, data will be on regular SAS.

Option 1:

R730 internal enclosure: PERC H730 with

(2) 960GB SSD 6Gbps SATA in RAID 1 and (8) 1.8TB 10k RPM 12Gbps SAS drives in RAID 10

Option 2:

R730 internal enclosure: PERC H730 with 

(2) 960GB SSD 6Gbps SATA in RAID 1

+

PowerVault MD1400: PERC H830 with

(8) 1.8TB 10k RPM 12Gbps SAS drives in RAID 10

[pcmeiners]

Some raid calculators, google......   raid calculator

https://techbast.com/2015/04/5-online-raid-calculator-tools.html   

take any calculator results as a guestimate, none factor in the mobo speed or specific adapters with specific parameters.

Dell adapter comparisons.....

https://www.dell.com/support/article/us/en/19/sln292279/perc-poweredge-raid-controller-types-for-del...   

Basically both controllers use the same LSI base adapter, have the same controller processing chip (same speed), but the 830 has faster ram.

Now if you do not exceed the adapters or the mobo system's bus bandwidth , the 10 drive array should be faster by > 10% due to the extra drives alone but there are many factors which affect throughput in benchmarks or an online system. The 830 has faster ram  so that should add a bit speed. Also the added drives (10 vs 8) adds a little more safety in raid 10 if a second drive fails before a dead drive is replaced .  Every Windows setup needs to be tweaked, Microsoft has a tweaking document for each server OS. As to 6 vs 12Gps  drives, I have not benchmarked the difference, from info on the web, likely marginal speed  difference.  Lastly, you need hot spares for the most safety for both arrays.