On 06/14/2013 12:34 AM, John Clark wrote: > Hi there, > > I'm new to kernel mailing lists so beg your pardon if I'm asking this > question in the wrong place or in the wrong way. > > Anyway, I'm tantalisingly close to getting my bcache-enabled system > up-and-running, but I've hit a brick wall which seems might be a bug > or undocumented performance limit of some kind. I'm hoping Kent or > others on this fine list can help. > > I have successfully created the following two RAID1 block devices, as > shown per /proc/mdstat: > > Personalities : [raid1] > md126 : active raid1 sdb[0] sdc[1] > 1953383360 blocks super 1.2 [2/2] [UU] > > md127 : active raid1 sdd[0] sde[1] > 117155200 blocks super 1.2 [2/2] [UU] > > /dev/md126 comprises two 2.0TB spinning HDD's which I'm intending to > use as a bcache backing device > /dev/md127 comprises two 60GB SSD's which I'm intending to use as a > bcache cache device > > So far so good. > > Creating the bcache superblock on the md127 appears to go smoothly: > > root@bigdata:~# make-bcache -C /dev/md127 > UUID: 1736b20f-6b85-4fee-a801-4cf7c1bba009 > Set UUID: b2c9e8e2-0606-4d51-bf9a-e9b8a6f150b3 > version: 0 > nbuckets: 228818 > block_size: 8 > bucket_size: 1024 > nr_in_set: 1 > nr_this_dev: 0 > first_bucket: 1 > > > Creating the bcache superblock on md126 *appears* to succeed also: > > root@bigdata:~# make-bcache -B /dev/md/spinning > > UUID: 9e2bd59a-a413-4ad2-a07b-6998dfa3e049 > Set UUID: 8c70baad-6941-4550-9fc8-b009e016b00d > version: 1 > block_size: 8 > data_offset: 16 > > However, the following is output on syslog when executing the above command: > Jun 14 14:21:37 bigdata kernel: [ 1602.102646] bcache: error opening > /dev/md126: Not enough buckets > > Indeed, although I can register the cache device (and the UUID shows > up in /sys/fs/bcache), all attempts to register the backing device > fails as follows: > > root@bigdata:~# echo /dev/md126 >/sys/fs/bcache/register > -bash: echo: write error: Invalid argument > > And, sure enough, the backing device UUID doesn't appear in > /sys/fs/bcache nor at /dev/bcacheN > > I've tried using the make-bcache -b parameter to specify a different > bucket size but I still get the same failure (unless I choose > ridiculously high or low bucket sizes, which results in bucket size > errors to be emitted on syslog). > > As I was just finishing up writing this and was about to hit SEND, I > noticed something that I wish I had noticed earlier - specifically > that the "bcache-3.2" section of the bcache git repo was last updated > 6 months ago. > > The kernel I'm running is built from that tree. I had assumed that it > was the version 3.2 kernel patched with a relatively current version > of bcache, but now I think I may be seriously mistaken and my problems > could be due to the possibility that I'm running an old and buggy > version of bcache. I don't want to get ahead of myself, but it seems a > decent guess that my problems might be stemming from the fact that the > 'bcache-3.2' tree uses old version of bcache. > > At the risk of getting seriously ahead of myself, assuming that my > problem is due to 'bcache-3.2' being out of date and buggy, I'll ask > this: what is the recommended way to get a current and stable version > of bcache running on a stable linux kernel? I'm wanting to use bcache > on a production system and so I'm a little wary of building the > 'bcache-for-3.10' tree. Ideally, I'd like to use bcache on a 3.2 > kernel, because that's the kernel version readily available presently > in debian stable/wheezy so I will be less likely to encounter kernel > version incompatibilities with my debian wheezy system. > > Many thanks in advance if anyone can help me along here. > > John > -- > To unsubscribe from this list: send the line "unsubscribe linux-bcache" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html Build from the 3.10 RC series. It may not be "stable" yet but should be within a few weeks I think and it has the bcache bits in it. I have been running from the bcache-for3.10 tree on CentOS 6 for a few months without any issues. I will be using the mainline 3.10-RC5 tree sometime over the weekend. -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
