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jtech007

Bought a used server, need some background on the backplane

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I picked up a Supermicro 4U 24 Bay server the other day. I was checking out the backplane and noticed it's an SAS model that is different from the SATA connections on the one that I bought years ago from Tam's.

 

The model number is SAS846EL2 and if I am reading the user guide correctly http://www.supermicro.com/manuals/other/BPN-SAS-846EL.pdf in some instances I should be able to control all 24 drives with one cable? Is that true and would I need a controller that will do all 24 drives with one connection? I run M1015's now but I am curious if this backplane would be superior to my SATA backplane with a lot less cables and maybe cards.

 

Edit: Looks like Tam's sold a similar one on eBay recently. http://www.ebay.ca/itm/Supermicro-24-Bay-Chassis-SAS846EL2-SAS-4U-JBPWR2-Server-/171348859970 Though it looks like a JBOD setup with the cards on the rear and no motherboard.

 

Any help or insight would be a big help. Thanks!

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Has a SAS expander built in, so yes all you need is one connection.

 

Having one drive per SAS channel would theoretically be faster assuming you have the PCIe channels avalable to the M1015 card(s) because there would be zero oversubscription, but using the SAS expander is nothing to dismiss because it is still pretty fast.  A lot of enterprise storage arrays run 48+ enterprise SAS drives on a 4 channel 6Gb SAS loop (technically dual loop with one loop per controller) and you would essentially be running only 24 drives on the same loop speed with a setup that doesn't even come close to the requirements of an enterprise array.

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Thank you for the reply!

 

So if I understand correctly the SAS backplane takes the place of say an Intel RES2SV240 expander? So I would run one cable from the M1015 to the backplane to control all 24 drives?

 

And in your opinion would 2-3 M1015's and my current SATA backplane be faster for 24 drives (eventually) and/or more ideal for unRAID and VM's or would the SAS expander backplane with one M1015 be a better solution? I am going to sell one chassis or the other just thinking through it all before I get rid of the other one.

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So if I understand correctly the SAS backplane takes the place of say an Intel RES2SV240 expander? So I would run one cable from the M1015 to the backplane to control all 24 drives?

 

More accurately, your 24 SAS backplane has SAS expander built into it.

 

And in your opinion would 2-3 M1015's and my current SATA backplane be faster for 24 drives (eventually) and/or more ideal for unRAID and VM's or would the SAS expander backplane with one M1015 be a better solution? I am going to sell one chassis or the other just thinking through it all before I get rid of the other one.

 

How many PCIe lanes do you have to each M1015?  24Gb/s is quite a bit of throughput...  3 M1015's sitting on enough PCIe lanes to service each full speed would *theoretically* have a higher ceiling on performance then the 24Gb/s on the 4 channel SAS port.  Are you going to be doing something that has more throughput then this and are you using an OS that is capable of driving this throughput?  If you were running several SSD's or a bunch of 15k drives then maybe.  Was thinking the PCIe 2.0 x8 on the M1015 capped out at around 32Gb/s

 

 

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How many PCIe lanes do you have to each M1015?  24Gb/s is quite a bit of throughput...  3 M1015's sitting on enough PCIe lanes to service each full speed would *theoretically* have a higher ceiling on performance then the 24Gb/s on the 4 channel SAS port.  Are you going to be doing something that has more throughput then this and are you using an OS that is capable of driving this throughput?  If you were running several SSD's or a bunch of 15k drives then maybe.  Was thinking the PCIe 2.0 x8 on the M1015 capped out at around 32Gb/s

 

I am currently running 2 M1015's on in 2 PCI-E 8x slots on an Asus M4A89GTD PRO Motherboard bought years ago for low power usage and inexpensive unRAID server. I am in the process of collecting new parts to venture in to the world of VM's through ESXI or Xen. I doubt I would ever use the SAS backplane for it's true intention which is high speed drives in an Enterprise environment. I just wanted to make sure I was not sitting on a great piece of hardware for unRAID and some VM's. It would seem that the SAS expander is overkill for what I need. Another similar chassis with the same backplane just sold for $500 on eBay tonight. Mine has that plus it's a working server with a lot of extras. Seems like it would make more sense to sell it an use the $ to buy parts that fit more with what I am going to use it all for, right?

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The true intention of that backplane is space efficiency and cost savings in an enterprise environment.  Servers tend to have a lack of IO space, thus using fewer PCIe cards for the same number of drives is important so you can have room for those other IO cards.  Or rather expensive RAID cards where having all drives on one card is necessary, thus the need for a SAS expander.  Or massive amounts of disks attached to each server, thus aggregation and over-subscription by using SAS expanders is almost necessary.

 

You are a home user so none of that applies.  Three M1015, or one with that backplane.  Either option will work just fine.  It really all comes down to what suites your needs the best.  Using a SAS expander will free up more PCIe slots for other use and using three M1015 will theoretically have more throughput and probably be slightly more cost effective but you will use up most if not all >=x8 lane PCIe slots on a single socket motherboard.

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The true intention of that backplane is space efficiency and cost savings in an enterprise environment.  Servers tend to have a lack of IO space, thus using fewer PCIe cards for the same number of drives is important so you can have room for those other IO cards.  Or rather expensive RAID cards where having all drives on one card is necessary, thus the need for a SAS expander.  Or massive amounts of disks attached to each server, thus aggregation and over-subscription by using SAS expanders is almost necessary.

 

You are a home user so none of that applies.  Three M1015, or one with that backplane.  Either option will work just fine.  It really all comes down to what suites your needs the best.  Using a SAS expander will free up more PCIe slots for other use and using three M1015 will theoretically have more throughput and probably be slightly more cost effective but you will use up most if not all >=x8 lane PCIe slots on a single socket motherboard.

 

Thank you for helping me sort it all out. I am 50/50 on keeping it as it would be nice down the road to have the option to have those PCIe slots open for other devices.

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