-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 When mdadm creates a raid5 array, it creates it in degraded mode. Then it kicks in the last device and runs the rebuild code, which reads from the other n-1 disks and writes to the nth disk as appropriate to satisfy parity requirements. This allows you to max out the write bandwidth on a single disk, and is the quickest way to make the array consistent. The speed reported by mdstat is the speed at which the array resync is completing. That is, it is the speed at which new areas of the disk are being brought into a consistent state. Because that speed is, absent other IO or high CPU load or other constraint, limited by the write bandwidth of your disk, that's what you're seeing. The speed decreases as you progress across the disk because the disk's write speed decreases across the disk. If you run iostat, you'll see that one of the raid's component disks is sequentially writing and the others are sequentially reading, all at the same speed (modulo a small amount of jitter caused by quantized timing). If you think about the algorithm involved, there's no faster way to do it, despite your initial gut feeling that an 8-disk array should be able to resync faster than that. - -Ben -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.5 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFGRSVMcsocGMHJ2H8RCt8mAKCYPDi6t0Zi4ZKxiJvWSg26L3vsoACfS3MD J8JTSSL3AukSprVlpLTJr50= =YZrE -----END PGP SIGNATURE----- - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
