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My PC case is put under the desk. I have many hard disks for storage and backups. I bought some "cages" which can hold 5 hard disks and mount a fan. And the cages are put on the desk (cable length around 1 meter), for easy swapping hard disks (while PC is off), and less dusty also.

This setup is already running. I am using (0.5 meter + 0.5 meter in serial) two SATA cables to connect from the motherboard to my hard disks on the desk. I know the length limit of SATA cable is 1 meter. This may be the reason why my hard disks sometimes disconnect, as I am pushing beyond its length limit (including the motherboard circuitry).

My ideal setup will be putting hard disks even further away than 1 meter, approaching 2 meters or even a bit more.

I have a few (not yet feasible) ideas:

  1. Any consumer grade SATA Signal Repeater? (I found the Renesas website. But they are not for home use.)
  2. If I convert SATA to eSATA at the motherboard, and convert back from eSATA to SATA at the harddisk, can the length limit go beyond 1 meter, and approaching around 1.8 meter? (eSATA length limit is 2 meter.)
  3. USB cables are much longer. And USB repeater (active USB cable, with power supplied) are very easily available. But converting SATA to USB3.0 seem slowing down the data transfer a lot. (But in the Wikipedia table, USB 3.0 could be as fast as SATA theoretically.)

Edit:

Thanks all the replies. I learnt a lot more.

  • My motherboard is relatively old. There are only USB 3.0 ports, no USB 3.1.

  • I am using cheap hard disks as I am doing RAID1. I just realise that their speeds are just only 230MiB/s.

  • Learnt from this webpage that USB3.0 typical transfer speed is around 300MB/s.

  • I was using SATA cables, not converting to USB connections for two reasons:

    1. It is because I felt USB was quite slow. However, it seems to be my misconception of my USB 2.0 experiences. Even if using USB 3.0 (300MB/s), the bottleneck is obviously the speed of my mechanical hard disks (230MiB/s).
    1. I want as least conversion as possible, and as few intermediate elements (e.g. USB to SATA convertor) as possible, in order to maintain the reliability. However, my currently 0.5m + 0.5m SATA cable connection is failing once a few days. It is already not reliable.

To sum up the points above, it is likely that converting to USB 3.0 seems to be the best solution. It allows me to hot swap the hard disks as well.

My setup would be (from PC) an Active USB3.0 extension cable, followed by a Powered USB 3.0 Hub, and lastly some USB3.0 to SATA3 convertor with power for each 3.5" mechanical hard disks.

Those three elements in the connection are powered (in another words, active) which I hope they would ensure stable connection. However using a USB hub is not a good idea. I will fall into the transfer speed bottleneck pitfall again. All the hard disks connecting to the hub will be limited to a sum of 300MB/s. (i doubt similar bottleneck applies to single USB connected DAS devices also.) Using a hub will get better cable management. OTOH to avoid bottleneck, I should connect each hard disk directly to the motherboard individually. (preferably to different USB controllers on the MDB also.)

Any things I need to be aware of? Among those three active powered electronics, there are many low quality copycats from less reputed companies. How can I choose the best ones?

Deleted as we should not ask how to choose a real world product here. Let us stay in the theoretical realm. Btw I have chosen a seems to be relatively reliable brand of "USB3.0 to SATA3 convertor with power". They had quite a lot of buyers but I do not see many complains of faulty copies.

midnite
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2 Answers2

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It depends on you minimum requirements. In layman's terms, if cable length and performance is important and the HD's only goes to one PC I would advice to implement SAN/iSCSI (that's what I use myself in such a scenario). If you need access for more then one PC a NAS would be the way to go and NAS is more common for personal setup then iSCSI. With both ways you can use one or multiple (via link aggregation) wired connections for greater performance then with a single cable.

Other then that you already know the alternative DAS options (USB-hub/USB, eSATA, and Thunderbolt might be an option as well). The problem with USB, SATA, etc. is that you can not scale performance easily, aggregation via Ethernet is much more common and less expensive other then that.

UPDATE: With the additional details in your question, I think DAS is the better option in your scenario (since your requirement for 2m length and USB 3.0 data throughput is quite moderate).

Albin
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I'm using eSATA to connect multiple 5.25" Blu-Rays drives and I think this 2m length limit is wrong. I use only 30cm SATA and 50cm eSATA cables and still have problems. Especially if I connect instead a Blu-Ray drive an usual HDD. I think because my eSATA PCIe slot adapter is a passive device (and more plugs means more loss).

Finally I'm thinking about using an alternative solution which works really good in my backup NAS. This server's motherboard has only 4 SATA ports, so I bought a cheap 1 to 5 SATA Port Multiplier to connect more HDDs. I never had problems with disconnects although the HDDs are connected through usual 30 + 30cm SATA cables. Maybe this is a form of "SATA amplifier" as the circuit board must be connected to a 5V power source (USB or SATA Power).

If you use one Port Multiplier for each drive, it could be a solution for your problem. You could "glue" the board under your table and connect it to an usual usb power supply. With one drive there is no relevant overhead: https://wiki.odroid.com/odroid-h2/application_note/10_sata_drives

"With SSD, sequential I/O speed reaches 500 MB/s."

mgutt
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