eSATA cards

[Charley]

So I've read the "Read this First" document and I'm curious about this statement:

"Avoid using SATA Port Multipliers at all costs. If you don't the cost is very likely to be "your data". These are error-prone and built by the lowest bidder and are about as reliable as you can expect."

I know a few people that are using SATA port multiplier cards (it seems the card of choice, currently is the Startech PEXESATA2, unless I'm mistaken) and haven't had any data loss issues. I'm curious about the evidence that supports that statement as I am in the final stages of using an eSATA connected external storage tower (Mediasonic ProBox HF2-SU3S2) attached to the above Startech port-multiplier card.

Will I really be playing Russian Roulette here? What is the actual issue behind this statement? If the issue is serious, then I'm sure I can find a way to pack my 4 disks into the case, but I'd rather not...

Thanks in advance!

 

[jgreco]

SATA port multipliers are generally poorly supported by FreeBSD. The companies that produce these wanna-sell-you-a-lower-cost-"RAID" typically don't put a lot of time and effort even into the Windows driver. We've seen them be problematic. That's basically the story.

Some companies like Backblaze have found golden paths to success, using carefully tested controllers and specific port multipliers and a particular version of Linux with a particular driver.

Also, external SATA enclosures are very risky to your pool, greatly increasing the chance of an inadvertent cable disconnect or power cycle event.

Further required reading:

https://forums.freenas.org/index.php?threads/port-multiplier-support.13499/

etc

 

[Charley]

Good info, thanks. Interestingly, I didn't find that thread when I searched for eSATA threads. I knew there had to be more useful info floating around here.

I did notice that when I put my server and Mediasonic in place, the eSATA cable easily detached from the back of my server when accidentally pulled. I don't expect that this would be an issue once it is live, however, it IS for home use and I have little ones that might find their way into my network rack and start pulling on things...

 

[jgreco]

Well, if you *have* to do it, make sure your entire pool is on the far end of the one cable.

 

[Charley]

Copy. I don't plan on spanning a pool across internal and external disks. It seems to me that the general problems I've read about are:

1. When a disk fails behind a port multiplier, the whole disk group is down until the failed disk is replaced (always or just a potential?)
2. High degree of possibility for data loss (though still not sure why that is, unless it is related to #1)
3. Little to no R&D for these cards, especially for FreeBSD

Sound about right?

 

[jgreco]

1) Unknown. Wouldn't be shocking, though. Obviously this might depend on the specific type of failure.

2) Probably more because losing only some disks in a pool can be particularly hazardous, so people who split between multiple units (internal, external) are at greater risk.

3) Correct.

 

[tom234679]

I had a recent experience with this and unfortunately did not see any horror stories before I got mine so here you go, here is my "hard lesson"

I got an esata card that supported a port multiplier because I was trying to save money. So I got me a Startech Esata card that supported a port multiplier. Bought an external enclosure that holds 4 drives, has a cooling fan on top. Seemed to be all set and fancy, I was rolling with 2 2 drive pools that were mirrored. My data by design seemed safe and all was well with the world. I was out only $180 for the setup and life was good.

Fast forward to 8 month later. I had a smart alarm for temperature on one of the drives, being that it was a mirror and all my data was replicated anyway I decided i would wait until it failed and then replace it. Here is where esata multipliers are the major suck.

The drive finally started failing on and off, which would be cool and all, except it was causing my other pool with all my really important stuff to keep re-silvering, because the one bad drive was causing my good drives to disconnect from from the server on and off. This went on for about 2 days as I went bazerk trying to figure out what was actually happening. The one drive that was actually bad only showed that it was running warm in smart data. And my drive that was perfectly fine was getting disconnected and causing a resilver. Also my smart data service hept crashing and would not start.

Eventually I decided to do more research on the effect of a failed drive on a port multiplier and bingo. One drive fails, it will cause the others issues. So I removed the bad drive and no more issues with the other drives in the enclosure.

Things that saved me was ZFS being good at scrubbing/re-silvering. Did not loose any data, which was really awesome. Also had that gone badly, I have a second freenas server that I use as a replica of my main freenas server.

I have since ordered
https://www.amazon.com/gp/product/B002QJZLCA/?tag=ozlp-20
https://www.amazon.com/gp/product/B00LSQOY6G/?tag=ozlp-20
which only totals to around $350 after i bought the 4 drive caddies to go with my drives.

So for $70 more I would have never had all of my precious data at risk. And to think i was about to buy a second external 4 drive multiplier and put more of my data at risk. After this lesson never again, would I ever, trust a esata port multiplier. I wish that someone had posted this post I just made, and I would have never have done what I did. My data is too important to me to trust something that can corrupt it.

 

[Ericloewe]

To be fair, several resources on the forum advise against most SATA controllers and categorically against SATA port replicators.

 

[tom234679]

To be fair, several resources on the forum advise against most SATA controllers and categorically against SATA port replicators.

Yea, I had seen very few comments about it when searching the freenas forums and no horror stories at all from the consequences like most other things had. I actually had seen a few positive posts as well. Which is why I made my post, because if I had seen it I would have never done what I did. Plus its time I start contributing some back to a community I have gained alot of info and a wonderful product from.

 

[Arwen]

Another "To be fair", it's a bit of combination of the SATA controller AND the associated SATA multiplier.
Meaning one might work okay, with a different partner. But, FreeNAS is about data availability and high
reliability. Thus, too much risk to use any SATA multipliers, and too much risk with certain SATA chipsets.

On the other hand, SAS expanders tend to be quite reliable. Your Lenovo disk tray probably has a SAS
expander in it.

All that said, I use an Intel SATA port built into my FreeNAS Mini, (ASRack C2750D4I), with an eSATA
PCIe panel adapter. Then use a cheaper dual disk SATA enclosure with both eSATA and USB 3.0 for my
backups. Stupid enclosure has builtin RAID, which I set to JBOD. That seems to work fine for my backups,
but I would not trust it for continuously attached disks.