# Configuration for 3 USB disks?



## dvdmandt (Mar 16, 2012)

Hi, I just bought 3 external 2TB disks, WD Elements. I was thinking about how to make the best use of them. My FreeBSD system is a bit old, Athlon 3200+ with 1GB ram. I have no problem upgrading the software.

I would preferr to be able to access my drives as a single volume (samba) and I would preferr to have some redundancy. The usage for this is a file dump for my home network where I will store backups and such, but I will also use it for some IO-intensive work.

What would you recommend in this case? RAID5+UFS? ZFS/RAID-Z? Are any of those even possible with external drives, or am I just asking for trouble here?


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## kpa (Mar 16, 2012)

Your hardware is bit limited for using ZFS but I think a 3 disk raidz1 pool could work if you do some tuning for ZFS on i386:

http://wiki.freebsd.org/ZFSTuningGuide#i386


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## SirDice (Mar 16, 2012)

It doesn't matter if the disks are internal, external, IDE, SATA, SCSI, Flash or anything else.

I do suggest using labels as USB disks tend to move around and order is important for RAID.


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## kpa (Mar 16, 2012)

The on-disk metadata is enough for ZFS to recognise which disk is part of which pool, even if the device names get suffled around it doesn't matter. It's of course nice to know which physical device corresponds to a device in a vdev if you have to replace a disk and that's where labels are very handy. The only exception to this is ZFS on root setup where a cached copy of zpool.cache is needed by loader(8) so that the kernel can import the pool before it tries to mount the root file system. (This is the reason why I avoid ZFS on root setups as much as possible).


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## shakky4711 (Mar 16, 2012)

> It doesn't matter if the disks are internal, external, IDE, SATA, SCSI, Flash or anything else.


In theory you are right, in practice I made bad experience with coupling FreeBSD and some USB controllers. 

Furthermore the maximum USB read-speed is ~25MB/sec. With direct connected SATA drives you get with standard or older hardware 65-100MB/sec, depending on the whole hardware constellation and the drives.

So I would strongly recommed to build ou the drives and connect directly by SATA.

Best regards
Shakky


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## SirDice (Mar 16, 2012)

shakky4711 said:
			
		

> Furthermore the maximum USB read-speed is ~25MB/sec. With direct connected SATA drives you get with standard or older hardware 65-100MB/sec, depending on the whole hardware constellation and the drives.


I didn't say it would perform, just that it works


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