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I wonder if installing (and running) Linux (CentOS, in this case) from a USB pendrive is a smart or stupid move.

Please note that:

  • I am talking about server environment, not clients;
  • I mean full OS install, not a read-only ISO-like boot image (ie: a "standard" install)

Practical example: a 8-bay server for ZoL duties, with 6x SATA disks and 2x SSD (for cache and SLOG). Would you install CentOS on a dedicated partition on the SSDs (with MD software RAID1) or using two (again, with MD RAID1) USB pendrives for OS install is a good idea?

Background information: reserving two disks for a RAID1 OS array is becoming relatively inefficient. After all, for a standard Linux install 32-64 GB are more that sufficient, but any SATA/SAS disk is much bigger than that. I am inclined to use two small-capacity SSDs where possible, but this means two disk slots are basically "thrown away". Another possibility is not using dedicated OS disks, instead relying on array/LVM partitioning to get the work done.

I was wondering if, with the ever-increasing USB pendrives capacities and low cost (ie: a 64 GB Toshiba-branded pendrive costs about €25), using a software-based RAID1 USB array is a good idea. In this manner, all disk slots can be dedicated to the data array itself (maybe using ZoL). After all, this is the exact setup used by many dedicated appliances (FreeNAS, for example) and something similar already exists in the form of embedded, RAIDed SD cards.

However, I often face client-grade USB support which is flacky at best (ie: the entire USB roots reset when under load) and I am somewhat concerned that server-grade USB roots/ports are not so much better. Moreover, I read about broken/flacky embedded SD cards and this can obviously happen with USB devices also.

Thanks.

shodanshok
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  • This is kind of "primarily opinion based" but I hope someone can post a few hard facts. My subjective view based on terrible experiences with dead pen drives: Avoid it like the plague if you don't have an OS with an embedded mode like eewhite describes in the linked question and even then I believe you are better off with a small SSD. Also check if your server doesn't have any internal mounting points for system SSDs or maybe an M.2 slot or similar. – Sven Dec 09 '17 at 11:40
  • Oh, and if you decide to go with the pen drive route anyway: Mirrored drives mean you will most likely need to use at least one external USB port (I've never seen more then one internal onboard USB-connector). In that case, use pen drives that are physically as a small as possible, reducing the chance that it gets moved accidentally when working on the cabling in a rack. – Sven Dec 09 '17 at 11:45
  • Oh, sure, I was thinking about external ports. Thank you for your input, Sven – shodanshok Dec 09 '17 at 12:34
  • That is why people have moved to OBR RAID1 and OBR RAID 10, with more disks OBR RAID 6 usually. – Damon Dec 10 '17 at 04:27
  • USB3 drives do this better than USB2 and I have a domestic fileserver that runs Debian in this way but I don't think I'd trust it on commercial servers, not least as anything that writes to the USB-mounted filesystem will probably cause increased load. I have considered running servers from PXE but you still have to reserve some space for persistence. – Simon Greenwood Dec 10 '17 at 08:49

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