On 07/09/12 13:23, Steven Chamberlain wrote:
[...]
> Plain UFS could be expected to be slow. Because it is unjournalled, I
> think metadata updates are forced to be synchronous.
On my amd64 box, plain UFS goes like greased lightning --- I was very
impressed. That's a much more modern hard drive, though (a spinning once).
[...]
> The `camcontrol identify ada0` command should show the status of a
> disk's write cache (and sysctl hw.ata.wc must also be 1). I think it
> will be 'on', but the sync updates of metadata might mean it is flushed
> regularly.
Apparently the eee SSD is pants:
device model SILICONMOTION SM223AC
[...]
Feature Support Enabled Value Vendor
read ahead no no
write cache no no
flush cache no no
overlap no
Tagged Command Queuing (TCQ) no no
Native Command Queuing (NCQ) no
SMART yes yes
microcode download no no
security no no
power management yes no
advanced power management yes no 0/0x00
automatic acoustic management no no
media status notification no no
power-up in Standby no no
write-read-verify no no
unload no no
free-fall no no
data set management (TRIM) no
It's a native SATA SSD with no TRIM! *cringe*
Turning softupdates on made the problem go away entirely; thanks. I had
previously wondered about this, but my last experience with softupdates
was on OpenBSD and that enables it via a mount option --- I didn't think
to look at tunefs...
$ time mkdir {0,1,2,3,4,5,6,7,8,9}{0,1,2,3,4,5,6,7,8,9}{0,1,2,3,4,5,6,7,8,9}
real 0m2.321s
$ time rmdir {0,1,2,3,4,5,6,7,8,9}{0,1,2,3,4,5,6,7,8,9}{0,1,2,3,4,5,6,7,8,9}
real 0m0.467s
Actually turning it on was an exercise in frustration, as you don't seem
to be able to use tunefs on a mounted file system and of course this was
my root partition... eventually I had to use a FreeBSD live USB image
and boot from that. Given what a vast difference it makes (more or less
the difference between a usable system and an unusable one, on the eee)
I would certainly suggest enabling it by default. Is there any reason
*not* to want softupdates?
I notice that my partitions do seem to be unaligned, but I don't recall
now whether I let the installer repartition my disk or not. As I don't
have TRIM anyway it's probably not important now.
[...]
> ZFS should of course be unaffected by the above issue, and be the
> best-performing choice of filesystem here.
Is ZFS viable on a 32-bit system? The FreeBSD wiki page on it (which,
being a wiki, is of course out of date, unrepresentative and probably
wrong) claims that these system is still prone to running out of memory
and panicking.
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