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I've done this for some NFS machines
(the ones I'm currently migrating to Ceph). It works... but I'm
moving back to small SSDs for the OS.
I used a pair of USB thumbdrives, in a RAID1. It worked fine for about a year. Then I lost both mirrors in multiple machines, all within an hour. I thought it was a bad batch, and made changes to make sure I used mirrors from different batches of drives. Then it happened again 6 month later. My best guess is that the automated manufacturing for these devices is so tight that the RAID1 wears them both out at exactly the same time. These drives have no controller, so they have no SMART data and no wear leveling. If you hotspot any part of the drive, you'll wear that part out very quickly. Make sure you don't use your swap at all, and make sure you mount those filesystem with noatime. It should have occurred to me sooner, but I should have followed a guide for booting off compact flash. I eventually made it work by switching to drives from different manufacturers, and attempting to verify that the actual flash chips are also from different manufacturers. It's a bit of work to figure out at the time, and it's something you need to re-verify every so often. For my Ceph cluster, I'm going back to SSDs for the OS. Instead of using two of my precious 3.5" bays, I'm buying some PCI 2.5" drive bays: http://www.amazon.com/Syba-Mount-Mobile-2-5-Inch-SY-MRA25023/dp/B0080V73RE , and plugging them into the motherboard SATA ports. The next chassis I buy will have some dedicated 2.5" bays, like this: http://www.supermicro.com/products/system/2U/6027/SSG-6027R-E1R12T.cfm (I see a lot of manufacturers starting to do this). The SSDs support SMART and wear leveling, and cheap SSDs are just a bit more than the 32GB thumb drives I was buying. Since it's just the OS, I don't need high performance SSDs, and I'm still following the compact flash booting guides to extend their lifetime. I am worried that I'll have the same problem with SSD mirrors failing at the same time. Since I can monitor wear leveling, I plan to retire the OS mirrors before the wear leveling runs out. Hi, what do you think to use a USB pendrive as boot disk for OSDs nodes? Pendrive are cheaper and bigger, and doing this will allow me to use all spinning disks and SSDs as OSD storage/journal. More over, in a future, i'll be able to boot from net replacing the pendrive without loosing space on spinning disks to store operating system _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com |
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