SSD transfer speed


J

Jan Stożek

Hi,

I measured transfer speed on my disk, which I use for some time
already, the result is here: http://bit.ly/1uojTNe.

Interestingly, the size of the ragged part, which is about 60%
of the disk's capacity, is (almost) exactly the size of my system
disk, while the other part of the disk, with almost uniform
performance, remains unused for some time already - though it HAD been
used previously. What is even more interesting, when sime time ago I
measured the disk performance after the system installed on the
*second* partition of the very same disk had been used for some time,
the graph looked almost exactly mirrored: it started with a degraded
performance on the initial sectors (like it is now), then there was a
large area of a pretty uniform, high performance representing the then
unused partition, followed by a ragged area of the partition in use.

Unfortunately, I do not have a screenshot to demonstrate it.

The system in question happens to be OpenSuse Linux, so most -
if not all - folders with significant amount of writes (/home, /var,
/srv, /swap) are located on magnetic drives or ramdisks. Noatime is
turned on, so I believe that the actual writes to the SSD are made
only during updates and upgrades. The disk is trimmed once a week
automatically.

The questions:
* Is this performance characteristic a significant symptom of a
wear?
* Is it dangerous to the data
* Can it be reversed anyhow?

The disk is Kingston SSDNOW 30GB. Performance was measured
using HD Tune run from Hiren's Diag CD, so it had nothing to do with
the drives. The computer in question is my home PC - used on a daily
basis, turned-off for the nights.

Thank you very much in advance for any hints.

--
Best regards,

(js).

PS. In case you prefer to responding directly, please remove the dash
with all subsequent letters from the email address.
 
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A

Arno

This is a result from disk-internal fragmentation, and no, there
is nothing reasonable you can do about it. Unless you have an
actual speed-problem, just ignore it.

Arno


Jan Sto??ek said:
I measured transfer speed on my disk, which I use for some time
already, the result is here: http://bit.ly/1uojTNe.
Interestingly, the size of the ragged part, which is about 60%
of the disk's capacity, is (almost) exactly the size of my system
disk, while the other part of the disk, with almost uniform
performance, remains unused for some time already - though it HAD been
used previously. What is even more interesting, when sime time ago I
measured the disk performance after the system installed on the
*second* partition of the very same disk had been used for some time,
the graph looked almost exactly mirrored: it started with a degraded
performance on the initial sectors (like it is now), then there was a
large area of a pretty uniform, high performance representing the then
unused partition, followed by a ragged area of the partition in use.
Unfortunately, I do not have a screenshot to demonstrate it.
The system in question happens to be OpenSuse Linux, so most -
if not all - folders with significant amount of writes (/home, /var,
/srv, /swap) are located on magnetic drives or ramdisks. Noatime is
turned on, so I believe that the actual writes to the SSD are made
only during updates and upgrades. The disk is trimmed once a week
automatically.
The questions:
* Is this performance characteristic a significant symptom of a
wear?
* Is it dangerous to the data
* Can it be reversed anyhow?
The disk is Kingston SSDNOW 30GB. Performance was measured
using HD Tune run from Hiren's Diag CD, so it had nothing to do with
the drives. The computer in question is my home PC - used on a daily
basis, turned-off for the nights.
 
J

Jan Stozek

Hi Arno,

Po głębokim namyśle Arno napisał w niedziela, 19 października 2014
19:10:
This is a result from disk-internal fragmentation, and no, there
is nothing reasonable you can do about it. Unless you have an
actual speed-problem, just ignore it.
The system actually runs like a dream, so my only concern was a
possible wear.

Thank you very much for your help.
 
Y

Yousuf Khan

Hi,

I measured transfer speed on my disk, which I use for some time
already, the result is here: http://bit.ly/1uojTNe.

Interestingly, the size of the ragged part, which is about 60%
of the disk's capacity, is (almost) exactly the size of my system
disk, while the other part of the disk, with almost uniform
performance, remains unused for some time already - though it HAD been
used previously. What is even more interesting, when sime time ago I
measured the disk performance after the system installed on the
*second* partition of the very same disk had been used for some time,
the graph looked almost exactly mirrored: it started with a degraded
performance on the initial sectors (like it is now), then there was a
large area of a pretty uniform, high performance representing the then
unused partition, followed by a ragged area of the partition in use.
I would guess that this performance degradation represents the deferred
TRIM writes no longer being deferred anymore. In a working system, there
is a normal amount of writes happening everywhere on the active part of
the disk. When an SSD is written to, it writes to unused flash memory
cells, and marks the old cells as ready for reuse later, through the
TRIM command. The idea being that after some idle time comes around,
it'll begin the process of zeroing the old cells, before putting them
back into the pool for reuse. During a benchmark, you might overload its
ability to leisurely reset these cells in its own time, and you end up
with cell recycling happening in the middle of actual operations.

Yousuf Khan
 
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J

Jan Stozek

Hi,

Po głębokim namyśle Mark F napisał w poniedziałek, 20 października
2014 00:16:
Backing up, initializing as appropriate for the device,
and restoring fixes most cases. (Do a real image backup
that doesn't attempt to move or defragment files if you want
to avoid system disk and licensing issues.)
Actually, I copied sector by sector the partition to itself
using Linux'es dd command, then trimmed, and accounted the full speed,
~188 MB/s +-1% across the whole drive. Didn't notice any impact on the
percieved speed of the computer though.
I run SpinRite on all drives, but am only showing the
HD Tune Pro 5.50 results for the SSD system disk.

The system disk has:
Firmware 2.15
(E7) SSD Life Remaining 0 (meaning 100%, I think)
(E9) Life Time Writes (NAND) 8385 GB
(EA) Life Time Writes (Host) 5905 GB
(F1) Life Time Writes 5905 GB
(F2) Life Time Reads 11436 GB
It's in SMART, isn't it? Unfortunately, for Kingstone those
params are not available. :(

Thank you very much for very detailed info. I must find
somewhere durability of my drive. ;)

--
Best regards,

(js).

PS. When responding directly, please remove dash with all subsequent
letters from the email address.
 

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