Comments on: ZFS Administration, Appendix B- Using USB Drives Linux. GNU. Freedom. Sun, 13 May 2018 18:21:35 +0000 hourly 1 By: Paranoin. Green Powe Mon, 29 May 2017 18:44:41 +0000 You say if saves energy! I am not sure of that.

Some USB sticks consume a lot of power, like Sandisk USB 3 64GiB, after five minutes of written a full virtual disk image backup (more than 10Gigabytes) it is so hot you can not touch it or you get burn.

So moving the head is less power than power used by such USB stick.

Anonymous: How much power uses your old (>500) usb sticks plus hubs? I understand you to not buy a SSD (no one give such great speed yet), but can you pay so much electricity bill (speculating on power)?

I had measure power for such Sandisk with a device that is set in middle, it drains more than 20 watts when writting at full USB 3 (5gb/s) speed... ihave no USB 3.1 Gen 2 (10gp/s) ports

By: Anonymous Mon, 29 May 2017 18:34:45 +0000 Are you using a USB 2.0 Hub on a USB 2.0 port?
What about using a USB 3 Hub on a USB 3 port? (and what about 3.0 versus 3.1 Gen2).

I mean, about using a lot of ols USB 2.0 Sticks on a HUB that is USB 3.x, would it pass beyond 40MB/s!

And what about IOPS (number of operations per second).

My tests (with EXT4) with more than five hundred old USB sticks give an impressive 9.5Gigabits/s.

By: Aaron Toponce Thu, 09 May 2013 14:44:59 +0000 Yes and no. First, ZFS is smart enough to know that the OCZ drives are faster than the USB sticks, so it will favor putting data there before using the USB drives. However, Having the USB drives will mean decreased seek latencies in retrieving data that would normally be on platter. So, it certainly doesn't hurt the pool at all, even if the USB sticks can't retrieve the data as quickly as the OCZ drives. But you are right that a cached page that once lived on the OCZ drives that now resides on the USB drives, will be accessed slower than before. But it's still faster than pulling it off platter for small random IO.

By: Jeremy Rosengren Thu, 09 May 2013 14:03:49 +0000 Question: It looks like you already have a couple of OCZ RevoDrives installed... in this particular scenario, do the USB cache devices still provide value? It does look like they're being used, does ZFS treat all the disks as the same speed, and if so, couldn't that hurt performance by having cache data written to devices that are slower than your SSDs?