On Jul 22, 2014, at 11:13 AM, Chris Murphy <[email protected]> wrote: > > It's been a while since I did a rebuild on HDDs,
So I did this yesterday and day before with an SSD and HDD in raid1, and made the HDD do the rebuild. Baseline for this hard drive: hdparm -t 35.68 MB/sec dd if=/dev/zero of=/dev/rdisk2s1 bs=256k 13508091392 bytes transferred in 521.244920 secs (25915056 bytes/sec) I don't know why hdparm gets such good reads, and dd writes are 75% of that, but the 26MB/s write speed is realistic (this is a Firewire 400 external device) and what I typically get with long sequential writes. It's probable this is interface limited to mode S200, not a drive limitation since on SATA Rev 2 or 3 interface I get 100+MB/s transfers. During the rebuild, iotop reports actual write averaging in the 24MB/s range, and the total data to restore divided by total time for the replace command comes out to 23MB/s. The source data is a Fedora 21 install with no meaningful user data (cache files and such), so mostly a bunch of libraries, programs, and documentation. Therefore it's not exclusively small files, yet the iotop rate was very stable throughout the 4 minute rebuild. So I still think 5MB/s for a SATA connected (?) drive is to be unexpected. Chris Murphy-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
