-----Original Message----- From: CentOS [mailto:centos-bounces@centos.org] OnBehalf Of Gregory P. Ennis Sent: Sunday, February 19, 2017 12:31 PM To: centos@centos.org Subject: Re: [CentOS] usb drives & Orico ORICO9548U3-BK

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I decided to build an archive server for thepurpose of backing up other fedora/centos desktops at theoffice. I built a machine and have installed Centos 7.3 on it with all updatescurrent. I also purchased a 3.0 usb sata drive cabinet (OricoORICO 9548U3-BK) and installed two 5T black WDdrives. There was no problem installing the usb cabinet or the drives. Iformatted each drive with xfs as /dev/sdc and /dev/sdd, and then combined theminto a software mirrored raid with mdadm as /dev/md0.

I've always thought that the perceived wisdom is tonot try and do software raid across USB - especially when both drives are atthe other end of the same USB cable. Sure USB 3 is faster and there's abetter chance it will appear to work at a reasonable speed, but it's notsomething I would contemplate.

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Everything was working perfectly until Iremoved the terminal, keyboard and mouse and tried to reboot themachine. It took a while to figure out, but when the mouse and keyboardwere removed the boot process assigns the usb drives differentlywhich makes /dev/md0 created by mdadm fail.

Which means that the drive letters are explicitlymentioned in /etc/mdadm.conf - you can change it to be wildcardedor leave mdadm to figure it all out itself. See 'manmdadm.conf'.

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My fstab file looks like :

/dev/mapper/centos_poar-root / xfs defaults 0 0 UUID=f915a354-28bf-4110-bec9-3767ef1fe52c/boot xfs defaults 0 0 /dev/mapper/centos_poar-home /home xfs defaults 0 0 /dev/mapper/centos_poar-u /u xfs defaults 0 0 /dev/mapper/centos_poar-swap swap swap defaults 0 0 /dev/sda /u0 btrfs defaults 0 0 # entries below were combined into one mirroredraid system

#/dev/sdc

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/u1 xfs defaults 0 0 #/dev/sdd /u2 xfs defaults 0 0 /dev/md0 /u1 xfs defaults 0 0

Another likely issue is that you explicitly mention/dev/sda in the fstab - if the drives are re-ordered, then /dev/sda will not bewhat you think it is. It's a much better idea to use UUIDs when mounting drives.You can find the UUID with

lsblk --fs /dev/sda

BTW, are you really using partitionless disks - isit really /dev/sda and not /dev/sda1 ?

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This works perfectly when a usb mouse and a usbkeyboard are attached, but when I remove the mouse and keyboard thesystem will not boot because the usb drives are relabeled as/dev/sda and /dev/sdb.

I would have thought that any SATA drives would havebeen processed before the USB drives - certainly it looks that wayon my system. Try going through the output of dmesg to see if you can seewhat is really happening when in the boot sequence.

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My thought is that if I could force the usbdrives to be labeled as /dev/sdc and /dev/sdd whether the mouse andkeyboard are attached or not, I might be able to fix the problem

It's much easier to make sure you don't explicitlyuse drive letters - because, as you've found out, they can change. Usefilesystem labels or UUIDs or disk IDs. The disk IDs can be found in /dev/disk/by-idand they should remain the same.

P.

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Pete,

Thank you for such excellent help; I appreciate yourwisdom and challenges. The machine I am working on is still at the 'lab'stage so everything can be changed at this point. I don't have the benefit of much 'perceivedwisdom' in that most of my knowledge comes from mistakes I havemade or mistakes others on this list have made that Ican learnfrom. So thanks again.

Here are some of my thoughts... right or wrong.

#1. 3.0 USB drives I originally performed some testing on a small usbpassport 3T drive and was amazed by the response and access times. I stumbled across the Orico cabinet during a NewEgg search, and decided to giveit a try. I was even more impressed with the response and accesstimes. I decided to attempt a mdadm raid on the the Orico and everything hasworked better than expected except for the problems I have had withdevice assignments. I did have an electrical failure at my home related to weather of which the ups powered down after 30minutes that caused one of the raid 5T drives to become corrupted. I reformatted the drive and rebuilt the raid with mdadm, and everything worked alot better than I expected. Iwill only be using this system to store *.tar.gz backup files from other systems. What should cause me to fear the USB 3.0 connection.

#2. /etc/mdadm.conf The tutorials I read about how to use mdadm did notinclude mdadm.conf, and this was not created when I installedmdadm. I will take a look at the man pages.... thank you.

#3. UUID's Thanks for the suggestion to use names instead ofdevice addresses and how to get the names with lsblk --fs /dev/sda. Using this should fix my problem of reassignment device names at boottime. Thanks much!!!

#4. Partitionless disks I orginally installed Centos 7.3 on an SSD, and theninstalled the hard drives subsequently. I noticed that I gained quite a bit of disc space by not using a partition. Since the files I will be storing on these discs are large and will only be accessed for archive purposes I wanted to use as much of the disk as possible. The original google searches I made related to using a partitionless disk did notgive me compelling rational to use a partition, however I would surely like tohear from you and others about this.

Thanks again for your help, and instruction!!!!!

I kinda did the same thing as you. I bought a 4TB WDElements. Disabled the sleep timer.

I use UrBackup to backup two local machines, one remote,to my CentOS server. The WD Elements is backing up the CentOS server as wespeak (since 9:00AM this morning).

I use a rsync script I found,https://github.com/laurent22/rsync-time-backup

I started with REAR, but it created a 1TB tar.gz file soI went with the rsync script. Had to remove the --one-file-system arg.