Need advice for DAS for my drives

[Fredrick]

Hi guys.

 

I'm currently running my drives (10 in number) through a LSI SAS-9201 16e card, and the drives are placed in a cheap chassis that has poor air flow, and is unsuitable for swapping drives etc. I've been looking for a used DAS/chassis that would better suit my needs. The server is a Proliant ML350 G6.

 

Well, an opportunity has presented itself. I can get two IBM EXP3000 for cheap, but as I've previously bought something that didn't work I'd like to check with you guys.

 

The specs are pretty thin, but the seller lists this:

- 2x Fibre Channel SAS controllere (39R6502)

- 2x ESM controller (39R6516)

 

From the pictures it seems one of them has both ESM-controllers, and one has both SAS-controllers

 

 

 

So my question is simple. Can I use these and hook them up to my LSI-card with a SFF-8088 cable?

 

Do I need a fiber HBA to use the one with SAS-controllers? (I only need one of them today, but in the future I'll likely get more drives)

 

How will the performance be compared to just running it from SFF-8088 to SATA cables I'm using today?

 

 

This opportunity will probably be gone tomorrow, so I hope someone with knowledge can confirm this will work. Searching the forum I found this thread which seems very positive

Edited September 16, 2017 by Fredrick

[Fredrick]

Well I can at least update here. 

 

I went for it as I felt it was a pretty good offer (about 100$ including one SFF-8088 cable and a HBA), and just got it fired up to test. I installed two brand new 8tb WD Reds (128mb cache), and started the preclear. I saw an average speed of about 180MB/s per drive which to me seems good. Obviously this wont be representative for the performance with 12 drives installed in each. 

 

As I've got two ESMs and two SAN-controllers, I'm not sure which is best. The ESMs are for redundancy, so I can probably have 1 of each in each of the EXP3000. This means I've already got all I need to hook up 24 drives to my system, awesome!

 

With regards to performance, I'd really like some input if you folks have knowledge. As far as I can tell the bottleneck for performance be the SAS cable at 6Gb/s (i think). That should be 62,5MB/s per drive, and is likely to be enough during normal operation. @johnnie.black states:

 

On 21.7.2017 at 10:03 AM, johnnie.black said:

Each x4 mini SAS link will have 2400MB/s bandwidth, of those 2200MB/s are usable, so if you use 2 HBAs, one for each EXP3000 you'll have around 180MB/s for each disk during parity checks/rebuilds (note: this with all SATA3 disks, using some SATA2 disks will bring the whole speed down), if you use a single HBA for both EXP3000 the bottleneck will be the x8 PCIe 2.0 slot, this can vary a little from board to board but in my experience ii's between 2500 and 3000MB/s, so you'd get around 100/125MB/s per disk during parity check/rebuilds.

 

 

Is this correct? How can i check the speed of my cable/link?

 

This also seems to me to be a better performance than I can achieve through the SAN-controllers at 4Gb/s?

[JorgeB]

5 minutes ago, Fredrick said:

Is this correct? How can i check the speed of my cable/link?

 

I believe the EXP3000 is SAS1/SATA2? if so it's half those speeds per link, you can see on unRAID at which speed disks are linking at, if it's SATA2 (300MB/s), each x4 mini SAS link will have 1200MB/s (1100MB/s usable).

[Fredrick]

Thanks for getting back to me

 

Unraid says this under Identity for the drives:

 

 

 

[JorgeB]

What matters is this:

 

Current: 3.0Gb/s

 

So it's SATA2.

[Fredrick]

That is very clear, thank you!

 

And just to confirm, this is more than what is available through the SAN-controllers?

 

Also with 8 lanes on the PCIe2.0 slot, this means I can run both EXP3000 from my single LSI SAS-9201 16e without having a new bottleneck. Right? (PCIe 2.0 x8 at 40Gb/s single direction)

[JorgeB]

58 minutes ago, Fredrick said:

this is more than what is available through the SAN-controllers?

 

Sorry, never worked or got info on SAN controllers, no clue.

 

58 minutes ago, Fredrick said:

Also with 8 lanes on the PCIe2.0 slot, this means I can run both EXP3000 from my single LSI SAS-9201 16e without having a new bottleneck. Right? (PCIe 2.0 x8 at 40Gb/s single direction)

 

Yes, it will use 2200MB/s max, usable bandwidth for a PCIe 2.0 x8 slot is around 2500 to 3000MB/s