Hello btrfs people, I am using btrfs to span across two SSDs at the moment. One is a 256GB and the other is a 128GB. So as of now, I have the data in "single" form and the metadata in a RAID1. I have heard that btrfs can adjust to some degree for devices in a RAID array that vary in sizes due to the way it handles things. But I feel as though the size difference between those two would be too vast to compensate for whatsoever. But I have an additional SSD in my machine, which is also a 128GB drive. I know that with RAID1, it will only duplicate the data no matter how many devices are present in the array. So if that is the case, if I were to add all three of my SSDs into the filesystem, and then put the data into a RAID1, would it be able to make use of all the space? The two smaller ones are about equal to the size of the larger, so in my mind it would seem that it would be entirely possible for it to keep two copies of each extent while still utilizing all the space. But I don't know if btrfs is set up to recognize this situation or how it would handle it. I know that I could potentially put the two smaller drives in some kind of an LVM or mdadm, but I would like to avoid this if possible. It just seems like an unnecessary layer of complexity. Though my question is about RAID1 specifically, as I would like to use the potential of the self healing features, I guess it would also extend to RAID0 as well. Would that be able to make efficient use of the space? Additionally, though not quite as much of a concern to me, the machine in which these drives live is an Ivy Bridge Laptop, so there are actually only two available SATA3 ports. The odd drive out at this point in time is actually an mSATA which is the only SATA2 port. If I were to add this to an array (assuming the above questions have favorable answers), how dramatically would the speed of the array be affected? To be honest, the speed of even just the mSATA drive alone is enough to keep me happy. But I have just been very curious about this. The write speeds of all three are relatively close. But the read speeds on the SATA3 are significantly faster than the mSATA. Anyway, thanks for the fantastic filesystem. Sorry for the long email, but these questions have been in the back of my mind for some time now. For the first question(s) at least I have not been able to find anything regarding that scenario. Regards, -- Curtis Shimamoto sugar.and.scruffy [at] gmail.com -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
