SATA SSD vs. SAS

[I.T.inColor]

Recently purchased a large number of 480GB datacenter grade SSDs with the idea to make a Napp-IT ZPOOL for a VM infrastructure. After receiving, I realized that they are SATA and not SAS, and that I'd completely overlooked that fact. I was planning on using them in a DELL R720XD which only uses two SAS cables for 24x2.5" disks. Since this backplane is obviously a SAS expander/multiplier, it will probably lead to disastrous results with SATA drives. Everything I've read says "don't use SAS expanders with SATA drives." (not to mention, that I'll completely saturate the data paths with these). In that vein, I've got a few questions.

People choose SATA for SSD, because when it comes to SSD, the price may be 4-10 times as much for SAS. I've seen lots of setups with SAS spinning disks and SATA for L2ARC or ZIL. How are people connecting SATA disks for just these tasks and avoiding problems? Straight onto the SATA port on the motherboard? Are there any SATA only controllers that work well for SSD on Omnios/OI?

Does anyone know of any JBODs that are expander/multiplier free that would work for this setup? I have had a hard time finding any.

Has anyone had any luck with interposers? I read this report, and it sounded promising till I got to the end.

RSF-1 High Availablity SSD pool for VM storage and Build space | XNAT Blog

Thanks in advance,

--
Nate

 

[wildchild]

Use a 9211 or m1015 and break out cables.
Is possible use a direct attached backplane.
Must confess i did have pretty much succes with dc3700's on a sas2 backplane too

 

[dba]

Recently purchased a large number of 480GB datacenter grade SSDs with the idea to make a Napp-IT ZPOOL for a VM infrastructure. After receiving, I realized that they are SATA and not SAS, and that I'd completely overlooked that fact. I was planning on using them in a DELL R720XD which only uses two SAS cables for 24x2.5" disks. Since this backplane is obviously a SAS expander/multiplier, it will probably lead to disastrous results with SATA drives. Everything I've read says "don't use SAS expanders with SATA drives." (not to mention, that I'll completely saturate the data paths with these). In that vein, I've got a few questions.

People choose SATA for SSD, because when it comes to SSD, the price may be 4-10 times as much for SAS. I've seen lots of setups with SAS spinning disks and SATA for L2ARC or ZIL. How are people connecting SATA disks for just these tasks and avoiding problems? Straight onto the SATA port on the motherboard? Are there any SATA only controllers that work well for SSD on Omnios/OI?

Does anyone know of any JBODs that are expander/multiplier free that would work for this setup? I have had a hard time finding any.

Has anyone had any luck with interposers? I read this report, and it sounded promising till I got to the end.

RSF-1 High Availablity SSD pool for VM storage and Build space | XNAT Blog

Thanks in advance,

--
Nate

Hi Nate,

I use SATA SSD drives with SAS backplanes and LSI SAS controllers very extensively and at extremely high loads (up to 96 drives, tens of thousands of MB/s and a million IOPS or more) with zero problems. I plug the SATA SSD drives into non-expander backplanes which connect to SAS HBAs. I have also used SAS expanders, though at lower loads.

 

[Pri]

I'm using an LSI 9260-4i RAID Card with an SAS HP 32 Port Expander. I use those with SATA disks exclusively and they work great. Never had a problem, more than two years running with this setup.

I've honestly never heard of this "Never use SATA with SAS Expanders" thing. Everything I've read on this matter says it works just fine if your HBA or RAID controller that the expander will be using supports SATA disks which 99.9% of them do.

 

[Patrick]

@dba - I think you also are not using Interposers which the linked article said was a major point of failure.

 

[Diavuno]

Many of my servers have sata (spinning and solid) drives on expanders. No issues.

 

[gea]

If you buy commercial storage, you are forced to use their controller and disks (mainly both SAS)

the reason is
- avoid problems, all combinations are tested (official reason)
- earn as much money as possible

If you buy storage with support, you are often forced to use SAS controller with SAS disks only

the reason is:
- avoid problems if possible (SAS is more tolerant to problems than Sata)

If you build your own:
- you should at least do some testings with your controller + disk combination.
SAS expander + Sata disk can work but problems are more probable than with SAS disks.
In the past there have been some problem reports (I have had also random unclear problems with WD raptors years ago) with expanders and Sata disks.

 

[Diavuno]

I recall several sata issues a well... But many concluded it had more to do with timing out.

That's why my production stuff is always bad firmware sata, or better. I'm mostly nearline these days, getting a good chunk of Seagate nas and we reds though.

 

[legen]

Can you do multipathing with SATA-drives on a SAS-HBA (i.e. share the drives between two machines in a cluster). Or does that require SAS drives?

 

[Mike]

You have multiplexing interposers but I think some expanders can also do this as a dual expander chassis might actually be doing it. I wouldn't want that level of complexity with Sata drives.

 

[wildchild]

Don't forget adding interposers could sometimes mean that the disk will no longer fit in the caddy or enclosure

 

[Diavuno]

I'd be curious to see if some "cluster in a box" setups require sas drives drives with dual lanes....

Would be interesting!

 

[Chuntzu]

SAS is a requirement for all the clusterinabox solutions for windows server 2012. Even those using the $6000 LSI syncro cards.

 

[Chuntzu]

Persistent reservations are needed in cluster environments to handle fencing. Sata drives don't have this command set.