Can a USB 2.0 drive handle HD recordings?

[CanadianEh]

Good evening,

My server is currently out of space for PATA drives, so I *might* go the route of adding a single external USB 2.0 drive for additional recording capacity. Would this be able to handle 2 HD recordings at a time?


Just curious... otherwise, I *might* go eSATA.... but that would require dropping a tuner to put in an eSATA PCI card


Thanks!
-Jay

[GKusnick]

USB 2.0 bandwidth is nominally 60 MB/s, which is comparable to typical drive transfer rates (internal or external). HD streams typically run about 2 MB/s. Seems like plenty of headroom to me.

On the practical side, I have three USB HD capture devices sharing a USB 2.0 hub, and have never had a problem recording three programs at once.

eSATA has higher bandwidth, but won't buy you much over USB for a single drive, since you'll still be limited by the drive's own transfer rate.

[CanadianEh]

Thanks Greg,

So one follow-up question. Are there any issues I should be aware of when using a USB-based drive for media storage when using SageTV in Service Mode? I guess I'm asking what would happen if the USB drive wasn't started up and available before Sage starts, after a reboot or something.....

[ybrew]

Originally Posted by CanadianEh

Thanks Greg,

So one follow-up question. Are there any issues I should be aware of when using a USB-based drive for media storage when using SageTV in Service Mode? I guess I'm asking what would happen if the USB drive wasn't started up and available before Sage starts, after a reboot or something.....

If a drive that you use for recordings is unavailable to sage, the recordings will still appear in the Sage Recordings, but you'll get an error during playback.

If you run comskip monitor, you'll get an error that a comskip drive is unavailable.

Reconnecting the USB drive would fix both of these errors.

[Sam]

Originally Posted by CanadianEh

I guess I'm asking what would happen if the USB drive wasn't started up and available before Sage starts, after a reboot or something.....

Sage is smart enough that when a given path in its folder list is not available, it temporarily hides recordings known to be in that path from the list you can view, but doesn't remove from its database unless it can find the path and the path no longer has the file(s) it expects.

So if the drive was not available, it obviously could not be used to store new recordings and you'd need to have space available in other path(s) in your setup configuration. So leave yourself at least one other path as a safety net; sage will place new recordings in the path with the most space available which presumably may be the external drive when it is online.

Whether the drive comes back after a reboot or power cycle seems to be dependent on the drive itself. One of mine does not; most do. I no longer use the one which does not, except as an archival drive (it is full anyway).

Regarding USB vs eSATA, I previously used an external tower with 8 PATA drives, using 4 pairs on USB 2.0 bridgeports running to a PCI card with 4 ports (no external hubs involved). I also have a couple of standalone external USB drives. I never had problems with recordings that I could contribute to the USB, even if I had two concurrent HD recordings. But they didn't necessarily happen on the same drive either.

That said, the sustained transfer rate on my USB drives tend to be about 21MB/s as measured by HDTach. But I've seen as low as 15MB/s. Everything was NTFS with 64K clusters.

I recently converted my external tower from USB2 to eSATA and now get 58-64MB/s transfer rates instead. I can now copy the files 3-4 times as fast, plus have RAID5 protection against single drive failures.

Note that most of my drives were always PATA drives; I just changed the interface. I put in a PCI card with 4 eSATA/SATA type II ports, and the card can handle up to 3 GB/s aggregate. Each port can accept up to a 5 port SATA II multiplier, meaning I can attach up to 20 drives to the card. It also does RAID0/1/5/10. On the back of each PATA drive I attached a small PATA to SATA converter (about $8 each from eBay). This lets me reuse my old drives but still have them attached via eSATA and be in RAID sets.

I currently have about 5TB online for much less than the cost of a NAS solution, and still have room to add more drives.

[ybrew]

Originally Posted by Sam

Sage is smart enough that when a given path in its folder list is not available, it temporarily hides recordings known to be in that path from the list you can view, but doesn't remove from its database unless it can find the path and the path no longer has the file(s) it expects.

That hasn't been my experience and is not what's in the faq.

I lost a drive recently. All the recordings on the drive were still listed. In order to remove them, I had to mount a new drive with the same drive letter. When I started sage back up, sage saw the empty path for the drive letter and removed the recordings. Until I did that, I could select recordings on the failed drive, but got an error when I tried to play them.

[Sam]

Originally Posted by ybrew

That hasn't been my experience and is not what's in the faq.

Hmm, been awhile since I did not have a drive online when I did it. I must mismember. I do know they aren't "lost" when the drive is not online, which is a good thing.

[stevech]

My measurement of USB2 drives showed that it was 1/3 the speed of IDE and SATA 2. Tests done on a fast PC, no USB1 devices, one cascaded hub. YMMV

For video big files needing 64K blocks, I don't thing the cheap CPU in the consumer NAS are good enough, nor is its file system under Linux. IMO.