iSCSI on USB HD: IMB TSM tells me: write errors

[cesco_78]

Hello!
I use a Freenas 8.2 and I've a problem with my storage.

The hardware is a DELL Precision and the storage is an external HD in a USB Box (750GB)
I Connected via iSCSI a Windows 2008R2 server with IBM Tivoli Sotrage Manager (backup system)

If I try to use the disk by Windows I've not problems, but, sometimes, when the TSM write on this disk i see a lot of write errors in TSM log and the system hangs.

In my old Freenas (version 7 with internal SATA hard drive) I had never errors.

The hard drive on the old FreeNAS is the same that I use in the new, it is onli in a USB BOX

Thanks for Your help!!

 

[jgreco]

So you've probably got dodgy USB connectivity. USB is one of those things... just because you *can* do something doesn't always mean you *should* or that it'll work well. Suggest you try connecting the drive via SATA. Then it'll either magically work, or maybe you'll find out the drive has some bad blocks or something like that which was causing the USB-SATA bridge to freak out.

 

[cesco_78]

I tried to connetc the hard drive by SATA, but the DELL is only IDE, and with 2 PCI2SATA card no hard drive worked :(

Thank you :)

 

[jgreco]

If your machine is old enough to be only-IDE, then it is very likely to be USB1 as well, and won't have sufficient throughput to keep up when the iSCSI target is busy. Might want to check that. If it's USB1, then I'd suggest you need to find a different server.

 

[cesco_78]

I'm sure that che USB connection is USB2, in performance graph I've 80Mbps throughput, that is over that 12Mbps of USB1.
I think that choosing an USB connetion was not a good idea :(

Thank You

 

[jgreco]

Given sufficient memory, it is possible to attain bursty speeds but still have the system slowly flushing out to disk. You'd probably notice it though. To be sure, you can check "dmesg" output.

usbus0: 12Mbps Full Speed USB v1.0
usbus1: 12Mbps Full Speed USB v1.0

usbus0: 480Mbps High Speed USB v2.0
usbus1: 480Mbps High Speed USB v2.0

One of the biggest reasons to avoid USB is that many USB-SATA bridge chips are dodgy (at best!), and particularly if there's something amiss with the drive, like maybe a bad sector, instead of handling it intelligently, it'll lock up or cause other problems.

You'll find that many Mac users avoid USB for storage like the plague it is. It can be insanely frustrating, especially when you have a vendor-supplied "external" variant of one of their drives, and it's acting stupid about a bad block or something like that. Nothing really compares to having a drive attached to an interface that was specifically designed for hard drives. We've also found that SATA-IDE bridges vary widely, but fortunately we don't see much IDE these days. ;-)

 

[cesco_78]

Thanks jgreco, i checked and is an USB 2, but i think that i need to buy an PCI-SATA cart to have a good system...