Re: can't mount RAID-1 btrfs after reboot
On Mon, 2009-08-31 at 01:09 +0200, Tomasz Chmielewski wrote: Jens Axboe wrote: I'm able to mount the filesystem by using /dev/sdb4: # mount /dev/sdb4 /mnt/btrfs/ After which I can unmount it, and use /dev/sda4 to mount the filesystem: # umount /dev/sdb4 # mount /dev/sda4 /mnt/btrfs/ Try btrfsctl -a first. It seems to do the trick. I suppose longer term, doing btrfsctl -a before mounting a (RAID) btrfs filesystem shouldn't be needed, or? Shorter term, writing a udev rule along the lines of ENV{ID_FS_TYPE}==btrfs, RUN+=/sbin/btrfsctl -A %N (put it in /etc/udev/rules.d/64-btrfs-scan.rules or so) will cause your btrfs to be scanned when found. Possibly something like this could be distributed with btrfsprogs? -- Calvin Walton calvin.wal...@gmail.com -- To unsubscribe from this list: send the line unsubscribe linux-btrfs in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: New idea about RAID and SSD
Massimo Maggi wrote: Hi, SSDs have low latency but a high price per GB, Traditional hard disks have high latency, but high sequential read/write speed and low price per GB. Is possibile to use a SSD for metadata, which requires many seeks and is relatively small, in a special RAID mode with a traditional hard disk for the extents of the real data? A cheap but performant SSD (maybe 32 GB) + a big and fast HD (maybe 1.5 TB, or two in RAID0 - 3TB ), wouldn't create an array much cheaper than a ssd-only array of the same size, and much faster (in not-only-sequential workload) than one or two traditional HDs in RAID0? Would it work? Thank you for your precious time! Massimo Maggi mass...@.it well, it is not a new idea. yes people are thinking about it, but it is not the most critical work on the list of things to do for btrfs or any other linux fs. jim -- To unsubscribe from this list: send the line unsubscribe linux-btrfs in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: New idea about RAID and SSD
Hello Massimo, Massimo Maggi wrote (ao): SSDs have low latency but a high price per GB, Traditional hard disks have high latency, but high sequential read/write speed and low price per GB. Is possibile to use a SSD for metadata, which requires many seeks and is relatively small, in a special RAID mode with a traditional hard disk for the extents of the real data? A cheap but performant SSD (maybe 32 GB) + a big and fast HD (maybe 1.5 TB, or two in RAID0 - 3TB ), wouldn't create an array much cheaper than a ssd-only array of the same size, and much faster (in not-only-sequential workload) than one or two traditional HDs in RAID0? Would it work? If you talk RAID0 (eg no redundancy), you could RAID0 one or several traditional disks, and use the SSD as a journal device. That would be ext3/4 only btw. With mdadm you could create a RAID1 and use --write-mostly: -W, --write-mostly subsequent devices listed in a --build, --create, or --add com- mand will be flagged as 'write-mostly'. This is valid for RAID1 only and means that the 'md' driver will avoid reading from these devices if at all possible. This can be useful if mirror- ing over a slow link. Where the 'slow link' would be the traditional disk. But this is raid1 and doesn't help in your case (but couldn't resist the need to mention it :-) Sander -- Humilis IT Services and Solutions http://www.humilis.net -- To unsubscribe from this list: send the line unsubscribe linux-btrfs in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html