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Old 08-23-2012, 03:00 PM
hvw59601
 
Default hibernate: swap on SSD = not fast

Hi,

Mindful of what Stan Hoeppner in various posts has written about SSD I
thought I'd put swap on an SSD I installed (Samsung SSD 830 128GB) in
order to get superfast hibernate.


Surprise: it is slower than usual and the disk light is on.

swap is here:

+ cat /proc/swaps
Filename Type Size Used
Priority
/dev/sdb3 partition 19535036
0 -1


which is on SSD:

...
/dev/sdb3: LABEL="SSD830.03" UUID="ede71620-d8fa-47fd-8aee-0e8b37f9e982"
TYPE="swap"

...

and this is the kernel cmdline:

BOOT_IMAGE=/SDB2.boot/vmlinuz-3.4.7-nodeb-amd64 root=LABEL=SSD830.02 ro
vga=791 nouveau.modeset=0 resume=LABEL=SSD830.03


Is there an explanation of this? It takes about 20s. to hibernate when
swap is on SSD.


Hugo


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Old 08-24-2012, 06:42 AM
Stan Hoeppner
 
Default hibernate: swap on SSD = not fast

On 8/23/2012 10:00 AM, hvw59601 wrote:

> Mindful of what Stan Hoeppner in various posts has written about SSD I
> thought I'd put swap on an SSD I installed (Samsung SSD 830 128GB) in
> order to get superfast hibernate.
>
> Surprise: it is slower than usual and the disk light is on.
[snip]
> Is there an explanation of this? It takes about 20s. to hibernate when
> swap is on SSD.

SSDs aren't magical white unicorns. They're just another SATA storage
device, albeit a fast one, and when problems arise you troubleshoot, as
with anything else.

This email mentions nothing of any troubleshooting performed by you up
to this point. It's sole purpose seems to be to blame me for what you
apparently believe is a bad recommendation.

Until you do basic troubleshooting we simply won't know what the problem
is. It could be any number of things that are fixable, hardware or
software related, or you could have a bad SSD. But I assure you the
problem isn't that hibernate to SSD is universally slow.

--
Stan


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Old 08-24-2012, 08:43 AM
Jon Dowland
 
Default hibernate: swap on SSD = not fast

On Fri, Aug 24, 2012 at 01:42:45AM -0500, Stan Hoeppner wrote:
> This email mentions nothing of any troubleshooting performed by you up
> to this point. It's sole purpose seems to be to blame me for what you
> apparently believe is a bad recommendation.

I read it very differently: veiled admiration and thanks for your expert
advice, and genuine surprise that things weren't working properly, with
a request for help in figuring out why. I'm in a very good mood right now
though, YMMV ☺


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Old 08-24-2012, 09:41 AM
Gaël DONVAL
 
Default hibernate: swap on SSD = not fast

Le jeudi 23 août 2012 à 10:00 -0500, hvw59601 a écrit :
> Hi,
>
> Mindful of what Stan Hoeppner in various posts has written about SSD I
> thought I'd put swap on an SSD I installed (Samsung SSD 830 128GB) in
> order to get superfast hibernate.
>
> Surprise: it is slower than usual and the disk light is on.

>From my very limited knowledge of how SSDs actually work, I wonder if
swapon actually trims your swap partition.


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Old 08-24-2012, 10:19 AM
Stan Hoeppner
 
Default hibernate: swap on SSD = not fast

On 8/24/2012 3:43 AM, Jon Dowland wrote:
> On Fri, Aug 24, 2012 at 01:42:45AM -0500, Stan Hoeppner wrote:
>> This email mentions nothing of any troubleshooting performed by you up
>> to this point. It's sole purpose seems to be to blame me for what you
>> apparently believe is a bad recommendation.
>
> I read it very differently: veiled admiration and thanks for your expert
> advice, and genuine surprise that things weren't working properly, with
> a request for help in figuring out why. I'm in a very good mood right now
> though, YMMV ☺

Bah, maybe I was being unnecessarily defensive. If so my apologies.

When I see my name specified on a worldwide mailing list, by someone
whose alias I don't recognize, followed by a complaint that something I
recommended isn't working, I guess I tend to assume the worst...

--
Stan


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Old 08-24-2012, 11:04 AM
Darac Marjal
 
Default hibernate: swap on SSD = not fast

On Thu, Aug 23, 2012 at 10:00:46AM -0500, hvw59601 wrote:
> Hi,
>
> Mindful of what Stan Hoeppner in various posts has written about SSD
> I thought I'd put swap on an SSD I installed (Samsung SSD 830 128GB)
> in order to get superfast hibernate.

I might be wrong here, but isn't the key benefit of SSDs that they have
a tiny access time? But that their read speed is about the same as a
normal disk (also, I might be wrong, but I understand their write speed
is average).

Hibernation, in contrast, is about writing out (and reading back) a
linear stream of data.

So, in summary, while SSDs may well help with swap performance, I'd not
expect them to be brilliant at hibernation.
 
Old 08-24-2012, 11:32 AM
Gaël DONVAL
 
Default hibernate: swap on SSD = not fast

Le vendredi 24 août 2012 à 12:04 +0100, Darac Marjal a écrit :
> I might be wrong here, but isn't the key benefit of SSDs that they have
> a tiny access time? But that their read speed is about the same as a
> normal disk (also, I might be wrong, but I understand their write speed
> is average).
This would have been true some years ago:

Comparison of average sequential reading rates (HDD of 2012 and SSD of
2011):
http://www.tomshardware.com/charts/ssd-charts-2011/AS-SSD-Sequential-Read,2782.html
http://www.tomshardware.com/charts/hdd-charts-2012/-01-Read-Throughput-Average-h2benchw-3.16,2901.html

Please note that I compared SSD with desktop HDD: mobile HDDs are
generally slower.

About write speed, the very best HDD gave 164.06MB/s on average while
*most* SSDs are above 150MB/s and the best reaches a few MB/s less than
400.

>
> Hibernation, in contrast, is about writing out (and reading back) a
> linear stream of data.
But you are right here: sequential read/write should be fast on HDDs as
well. But with and SSD twice as fast as the previous HDD, you would
still expect suspend time to be cut off by a factor of 2.

>
> So, in summary, while SSDs may well help with swap performance, I'd not
> expect them to be brilliant at hibernation.
Seems right.



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Old 08-24-2012, 11:58 AM
Darac Marjal
 
Default hibernate: swap on SSD = not fast

On Fri, Aug 24, 2012 at 01:32:16PM +0200, Gaël DONVAL wrote:
> Le vendredi 24 août 2012 à 12:04 +0100, Darac Marjal a écrit :
> > I might be wrong here, but isn't the key benefit of SSDs that they have
> > a tiny access time? But that their read speed is about the same as a
> > normal disk (also, I might be wrong, but I understand their write speed
> > is average).
> This would have been true some years ago:
>
> Comparison of average sequential reading rates (HDD of 2012 and SSD of
> 2011):
> http://www.tomshardware.com/charts/ssd-charts-2011/AS-SSD-Sequential-Read,2782.html
> http://www.tomshardware.com/charts/hdd-charts-2012/-01-Read-Throughput-Average-h2benchw-3.16,2901.html
>
> Please note that I compared SSD with desktop HDD: mobile HDDs are
> generally slower.
>
> About write speed, the very best HDD gave 164.06MB/s on average while
> *most* SSDs are above 150MB/s and the best reaches a few MB/s less than
> 400.

Ah, my knowledge was out of date. I'll try and squirrel away that
factoid
 
Old 08-24-2012, 12:29 PM
Gaël DONVAL
 
Default hibernate: swap on SSD = not fast

Le vendredi 24 août 2012 à 12:58 +0100, Darac Marjal a écrit :
> On Fri, Aug 24, 2012 at 01:32:16PM +0200, Gaël DONVAL wrote:
> > Le vendredi 24 août 2012 à 12:04 +0100, Darac Marjal a écrit :
> > > I might be wrong here, but isn't the key benefit of SSDs that they have
> > > a tiny access time? But that their read speed is about the same as a
> > > normal disk (also, I might be wrong, but I understand their write speed
> > > is average).
> > This would have been true some years ago:
> >
> > Comparison of average sequential reading rates (HDD of 2012 and SSD of
> > 2011):
> > http://www.tomshardware.com/charts/ssd-charts-2011/AS-SSD-Sequential-Read,2782.html
> > http://www.tomshardware.com/charts/hdd-charts-2012/-01-Read-Throughput-Average-h2benchw-3.16,2901.html
> >
> > Please note that I compared SSD with desktop HDD: mobile HDDs are
> > generally slower.
> >
> > About write speed, the very best HDD gave 164.06MB/s on average while
> > *most* SSDs are above 150MB/s and the best reaches a few MB/s less than
> > 400.
>
> Ah, my knowledge was out of date. I'll try and squirrel away that
> factoid
>

But you comment still holds true: one should not expect a huge increase
of performance here as far as hibernation is concerned.


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Old 08-24-2012, 01:25 PM
Gary Dale
 
Default hibernate: swap on SSD = not fast

On 24/08/12 08:29 AM, Gaël DONVAL wrote:

Le vendredi 24 août 2012 à 12:58 +0100, Darac Marjal a écrit :

On Fri, Aug 24, 2012 at 01:32:16PM +0200, Gaël DONVAL wrote:

Le vendredi 24 août 2012 à 12:04 +0100, Darac Marjal a écrit :

I might be wrong here, but isn't the key benefit of SSDs that they have
a tiny access time? But that their read speed is about the same as a
normal disk (also, I might be wrong, but I understand their write speed
is average).

This would have been true some years ago:

Comparison of average sequential reading rates (HDD of 2012 and SSD of
2011):
http://www.tomshardware.com/charts/ssd-charts-2011/AS-SSD-Sequential-Read,2782.html
http://www.tomshardware.com/charts/hdd-charts-2012/-01-Read-Throughput-Average-h2benchw-3.16,2901.html

Please note that I compared SSD with desktop HDD: mobile HDDs are
generally slower.

About write speed, the very best HDD gave 164.06MB/s on average while
*most* SSDs are above 150MB/s and the best reaches a few MB/s less than
400.

Ah, my knowledge was out of date. I'll try and squirrel away that
factoid



But you comment still holds true: one should not expect a huge increase
of performance here as far as hibernation is concerned.

For a fast hibernate, sequential write speed is the key benchmark. The
Samsung 830 is supposedly very fast at this. However, the original
poster complained that hibernation is actually slower. This is the issue
that should be discussed.


So why would switching to an SSD slow hibernation times? Frankly I can't
think of any reasons (comparing apples to apples) why a faster drive
should lead to slower performance. Possibly it's an interface issue -
the SSD's controller is getting swamped - while the HDD the poster had
been using was able to handle a faster continuous write.


However, I can't find any evidence for this in the TomsHardware benchmarks.



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