RAID controller question

[Lord Mirdalan]

I'm looking at this RAID controller: https://www.wiredzone.com/shop/product/10021897-supermicro-aoc-s2308l-l8e-8-ports-sata-sas-6gb-s-pci-e-raid-card-4216?page=3&category=116

I know that is uses SAS, but is it mini-SAS? 

 

And if yes, I'm asking for an idiot-check here. Could I take this cable: https://www.amazon.com/gp/product/B012BPLYJC/ref=ox_sc_act_title_1?smid=A1AMUYYA3CT6HJ&psc=1 And use it to connect a few HDDs?

 

Sorry for the basic questions, but I;m not really sure where to look for answers. 

[Electronics Wizardy]

1 minute ago, Lord Mirdalan said:

know that is uses SAS, but is it mini-SAS? 

mini sas is those connectors on the back of the card.

 

1 minute ago, Lord Mirdalan said:

And if yes, I'm asking for an idiot-check here. Could I take this cable: https://www.amazon.com/gp/product/B012BPLYJC/ref=ox_sc_act_title_1?smid=A1AMUYYA3CT6HJ&psc=1 And use it to connect a few HDDs?

Yup that cable will work fine.

 

Id probably get a different raid card like a used dell h700, cheaper and the same chip + performance.

 

Also you probably want to get the battery for the card for best performance.

[LIGISTX]

I guess first question.... why do you need a RAID controller? What’s the application and use case? Just want to make sure your going down the correct path for your needs. 

[Lord Mirdalan]

So is there a non-mini SAS?

 

What do you mean by "the battery"?

 

Thanks for the help!

[Electronics Wizardy]

Just now, Lord Mirdalan said:

So is there a non-mini SAS?

 

What do you mean by "the battery"?

 

Thanks for the help!

There are lots of different sas connectors, depending on the speed and whats being connected.

 

Raid cards have a battery so they can use a write cache. If the battery isn't present, the write performance may be very bad.

 

What raid setup do you plan on using?

[Lord Mirdalan]

9 minutes ago, Electronics Wizardy said:

There are lots of different sas connectors, depending on the speed and whats being connected.

 

Raid cards have a battery so they can use a write cache. If the battery isn't present, the write performance may be very bad.

 

What raid setup do you plan on using?

So by battery do you mean a chemical battery that stores electricity? Or do you mean some RAM that serves as a write cache? The Dell controller you referenced looks to have some DDR2 attached to it. 

 

I'm planning to use UnRAID, as that's right about at the level of complexity I can handle. 

[Electronics Wizardy]

1 minute ago, Lord Mirdalan said:

So by battery do you mean a chemical battery that stores electricity? Or do you mean some RAM that serves as a write cache? The Dell controller you referenced looks to have some DDR2 attached to it. 

 

I'm planning to use UnRAID, as that's right about at the level of complexity I can handle. 

If your using unraid, you want a hba, not a raid card then. THen a battery won't be needed.

 

Id get one of these  https://www.ebay.com/itm/DELL-H310-W-2-x-CABLES-FLASHED-LSI-IT-MODE-9211-8i-SAS2008-ZFS-UNRAID-TRUENAS/313273295443?epid=12037689214&hash=item48f08b2253:g:VLAAAOSw4vpeJLrq Or a simmilar model.

[Lord Mirdalan]

44 minutes ago, Electronics Wizardy said:

If your using unraid, you want a hba, not a raid card then. THen a battery won't be needed.

 

Id get one of these  https://www.ebay.com/itm/DELL-H310-W-2-x-CABLES-FLASHED-LSI-IT-MODE-9211-8i-SAS2008-ZFS-UNRAID-TRUENAS/313273295443?epid=12037689214&hash=item48f08b2253:g:VLAAAOSw4vpeJLrq Or a simmilar model.

Thank you for catching my mistake, I wasn't aware of the difference between a HBA and a RAID controller. 

 

A tip of the hat to you, @Electronics Wizardy

[LIGISTX]

8 hours ago, Lord Mirdalan said:

Thank you for catching my mistake, I wasn't aware of the difference between a HBA and a RAID controller. 

 

A tip of the hat to you, @Electronics Wizardy

Thus why I asked why you need a RAID controller   

 

Unraid and Freenas (ZFS) and such use software RAID. They want bare metal access to the drives. Piping the drives through a RAID controller removes their ability to do their magical software RAID.

 

There are many RAID controllers you can flash to IT mode which effectively turns them into HBA’s, this is the typical solution as enterprise RAID cards are rock solid, and when in IT mode they do what you want in a software RAID deployment. 

[Nick7]

5 hours ago, LIGISTX said:

Unraid and Freenas (ZFS) and such use software RAID. They want bare metal access to the drives. Piping the drives through a RAID controller removes their ability to do their magical software RAID.

That's not really true.

ZFS and unraid can use drives behind proper RAID card. But, there's:

1) no need for such thing, as both have their own redundancy they use

2) it's better unraid/ZFS use their own checks to fix any possible errors

 

Basically, there's no benefit at all using proper RAID card with ZFS/unraid.

So make your life simpler and get HBA for that.

 

From what I gather, you need just SATA ports?

Why not get simple SATA PCIe card instead?

[LIGISTX]

8 hours ago, Nick7 said:

That's not really true.

ZFS and unraid can use drives behind proper RAID card. But, there's:

1) no need for such thing, as both have their own redundancy they use

2) it's better unraid/ZFS use their own checks to fix any possible errors

 

Basically, there's no benefit at all using proper RAID card with ZFS/unraid.

So make your life simpler and get HBA for that.

 

From what I gather, you need just SATA ports?

Why not get simple SATA PCIe card instead?

They “can”, but you really, REALLY, do not want anything between freenas and your drives. Will it work, yes... does your chance of catastrophic failure also go up.... yes. 
 

Besides providing no benefit, a RAID card interferes with ZFS’s ability to manage everything. Just because it boots and works doesn’t mean it’s a good deployment strategy. 

[LIGISTX]

Quick google, this is a decent little thread. 

 

Always want to give ZFS bare metal access. Especially if your planning on buying components.... Don’t buy the wrong tool for the job. Any tool can be a hammer, but hammers work best as hammers. 
 

https://serverfault.com/questions/545252/zfs-best-practices-with-hardware-raid

[Nick7]

On 2/5/2021 at 6:51 PM, LIGISTX said:

They “can”, but you really, REALLY, do not want anything between freenas and your drives. Will it work, yes... does your chance of catastrophic failure also go up.... yes. 
 

Besides providing no benefit, a RAID card interferes with ZFS’s ability to manage everything. Just because it boots and works doesn’t mean it’s a good deployment strategy. 

 

On 2/5/2021 at 8:59 PM, LIGISTX said:

Quick google, this is a decent little thread. 

 

Always want to give ZFS bare metal access. Especially if your planning on buying components.... Don’t buy the wrong tool for the job. Any tool can be a hammer, but hammers work best as hammers. 
 

https://serverfault.com/questions/545252/zfs-best-practices-with-hardware-raid

There are quite a few misconceptions about ZFS and 'bare metal' access to drives.

ZFS does NOT have ability to read things like SMART or similar, so bare access is NOT required, nor does it have any advantage.

Using RAID controller in front of ZFS is not a problem at all, nor does increase chance of catastrophic failures, as long as you do not make major mistakes.

 

ZFS has advantage against standard RAID controllers due to checksum checking in case there is fault in RAID. With checksums it can detect which drive still has proper working data, if there's error on disk. RAID controllers may silently read errors (like so often quoted bit rot issue).

In enterprise storage systems this is combated again with checksums, and one of reason why some drives are formatted with 520 bytes sectors, or even more.

 

Back to ZFS - having 'bare metal' access will not make that field more reliable, nor safer, compared to ZFS RAID where you create one logic vdisk on each physical disk.

What you do want to avoid is creating RAID0/1/5/6 on RAID controller itself. You want to pass drive as it (one vdev over one whole drive) to ZFS, so ZFS uses checksuming on those disks instead of RAID controller.

 

Also, you *can* use writeback on RAID card in this case, as it *will* improve overall ZFS performance, but you must have battery too. Same applies as with other filesystems.

 

Again, even if you do make any major mistakes, ZFS's scrub system is quite good, and can detect if there are any 'silent' errors too.

 

Bottom line, it's easiest to use 'bare metal' disks. Using disks thru RAID controller is fine too. Using RAID0/1/5/6 on RAID controller, and passing that to ZFS is not recommended, but yes.. it will work, but again - WHY make your life harder?

 

Issue with this is often over exaggerated, same as 'required ECC memory', and so many times quoted '1GB RAM for 1TB of HDD'.