Haven't seen much traffic on the list, maybe everybody is still recovering from turkey comas (at least in the US ;) ). No thoughts on this issue? Am I misunderstanding the purpose of the -w argument, is it not intended to align with the SSD page size? > -----Original Message----- > From: Paul Henson [mailto:paul.b.henson@xxxxxxxxx] On Behalf Of Paul B. > Henson > Sent: Friday, November 29, 2013 7:38 PM > To: linux-bcache@xxxxxxxxxxxxxxx > Subject: register_bcache() error opening /dev/md2: bad block/bucket size > > I'm trying to set up a mirror of two Samsung 840 Pro 256GB SSDs as a > cache device. Per their specs, the page size is 8k, and the erase block > size is 1024k, so I created the cache device as: > > make-bcache --wipe-bcache -b 1024k -w 8k -C /dev/md2 > > With a bucket size equal to the erase block, and a block size equal to > the page size. The documentation on block size wasn't really clear, but > I believe it's supposed to equal the ssd page size, ie, the minimum io > size for the device. > > However, when trying to register this cache device, it fails with: > > bcache: register_bcache() error opening /dev/md2: Bad block/bucket size > > Looking at the code: > > err = "Bad block/bucket size"; > if (!is_power_of_2(sb->block_size) || > sb->block_size > PAGE_SECTORS || > !is_power_of_2(sb->bucket_size) || > sb->bucket_size < PAGE_SECTORS) > goto err; > > and given PAGE_SIZE = 4096 and PAGE_SECTORS = 8, it's complaining that my > cache device block size of 8k is greater than the page size of 4k. I guess > I could create my cache device with a block size of 4k to make it work, but > that seems inefficient as it does not match the page size. What's this > limitation about? Can it be changed? Are SSD's with a > 4k page size just > poor choices for a cache device? > > Thanks... -- 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
