Mark Lord wrote:
Phillip Susi wrote:
Sounds like this is a serious bug in the WD firmware.
For personal systems, yes. For servers, probably not a bug.
Disabling readahead means faster execution queued commands,
since it doesn't have to "linger" and do unwanted read-ahead.
So this bug is a "feature" for random access servers.
And a big nuisance for everything else.
I think you misunderstand the bug. The bug is not that the drive
disables internal readahead; the bug is that host supplied readahead
requests work so horribly. It is a good thing that the drive allows the
host to control the readahead, but something is wrong if the drive's
readahead is WAY better than any the host can perform.
In other words, if the host is sending down multiple sequential reads
such that the queue always has a request for the next sector, the drive
should be hitting its maximum physical transfer rate. If it doesn't,
then something is very broken with its firmware.
It is still possible though, that the kernel is simply not issuing its
own readahead effectively so the queue ends up empty at times and the
disk goes idle. This would be worth investigating before letting WD
know they have a serious firmware problem.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
