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DKS
Damn Kidney Stones
Premium,ExMod 2002
join:2001-03-22
Owen Sound, ON
kudos:2
reply to dave

Re: [WIN7] Recommended SSD System Tweaks?

said by dave:

said by DKS:

Drive alignment is irrelevant for SSD's.

Not so. SSDs read/write data based on their notion of an internal block size, and the OS read/writes data based on its notion of a cluster size. You don't want OS clusters misaligned with respect to SSD blocks, since otherwise one OS write can require modifications to two SSD blocks: performance goes way down.

But Windows 7 handles that correctly. Previous versions got it consistently wrong (because they started the first partition something like 63 sectors in from the beginning of the disk).

Fred Langa at Windows Secrets did comprehensive testing this week (unfortunately it's behind a paywall or I would link it) and showed that drive alignment makes zero difference in an SSD.

quote:
The throughput times of the misaligned-versus-aligned SSD produced the following results:
Random-access read
Before alignment: 149.2 megabytes per second (MBs)
After alignment: 150.0 MBs
Sequential read
Before: 278 MBs
After: 277 MBs
Windows Experience Index
Before and after: 7.9 (The scale goes only to 8.) Bootup and shut down
No perceptible change.
And so on

In every area I looked at, I could detect no meaningful difference in the SSD's aligned and misaligned performance.
These results make sense if alignment-performance issues are mostly related to drive mechanics. When a traditional platter drive is misaligned, its heads might have to make additional movements to completely read or write data to each sector. With a single file using hundreds or even thousands of sectors, those extra movements could add up to a significant amount of time.

SSDs, on the other hand, have no platters or heads. Whether the sectors are aligned or not, accessing different memory addresses in an SSD's RAM takes almost no time at all. So it's not surprising that aligning the sectors on my SSD showed no significant performance improvement.

Drive alignment might have better results with other configurations heavy, constant database lookups; conventional, mechanical drives; or RAID systems. Your results might also be different if your drive is formatted with tools that handle alignment differently or not at all.

--
Need-based health care not greed-based health care.


JohnInSJ
Premium
join:2003-09-22
Aptos, CA
Is it just me or did Fred test the wrong thing.

If not aligned, WRITEs are a problem
- a write can cause two SSD blocks to need to be updated, which is an unnecessary update to a flash memory block. Life-1 for no reason
- a write update to two blocks is going to take more time than a write to one block

So, testing read speeds is going to show either of these things how, exactly?
--
My place : »www.schettino.us


DKS
Damn Kidney Stones
Premium,ExMod 2002
join:2001-03-22
Owen Sound, ON
kudos:2
said by JohnInSJ:

Is it just me or did Fred test the wrong thing.

If not aligned, WRITEs are a problem
- a write can cause two SSD blocks to need to be updated, which is an unnecessary update to a flash memory block. Life-1 for no reason
- a write update to two blocks is going to take more time than a write to one block

So, testing read speeds is going to show either of these things how, exactly?

You might find this thread helpful in response to Fred's comments:

»windowssecrets.com/forums/showth···e-drives

Frankly, it seems to be, for most people, searching after the Holy Grail. And except for the very technical or extremely anal, not to amount to a hill of beans.
--
Need-based health care not greed-based health care.


JohnInSJ
Premium
join:2003-09-22
Aptos, CA
The linked comments say exactly what I said, with more words

Write is the issue, not read. Slight but possibly insignificant in modern SSD increase in wear. Two read/writes vs 1... two REALLY FAST R/Ws, but still, double the time. For Writes. Sometimes. So Fred tested the wrong thing (read speed)
--
My place : »www.schettino.us

dave
Premium,MVM
join:2000-05-04
not in ohio
kudos:8
Reviews:
·Verizon FiOS

1 edit
reply to DKS
It so happens that I often chat to a senior guy where I work whose job in part involves figuring out the impact of various disk technologies on our product line. And he tells me it does make a difference. Unfortunately his reports aren't public.

Misalignment is mostly a write problem, and more so on a not-new drive. (You can't overwrite an SSD block; the controller needs to allocate an erased block, and schedule the old one for erasure.)

FWIW, not all SSDs are equal. Different controllers choose to optimize for (note rare example of correct usage of the word) different scenarios.


DKS
Damn Kidney Stones
Premium,ExMod 2002
join:2001-03-22
Owen Sound, ON
kudos:2
said by dave:

It so happens that I often chat to a senior guy where I work whose job in part involves figuring out the impact of various disk technologies on our product line. And he tells me it does make a difference. Unfortunately his reports aren't public.

Misalignment is mostly a write problem, and more so on a not-new drive. (You can't overwrite an SSD block; the controller needs to allocate an erased block, and schedule the old one for erasure.)

FWIW, not all SSDs are equal. Different controllers choose to optimize for (note rare example of correct usage of the word) different scenarios.

In that situation, I can understand the requirement. But for the 99% of consumers, not so much. Let Windows 7 do its thing and the rest of us should be fine. After several drive failures (OCZ) I have been using Intel SSDs with no problems.
--
Need-based health care not greed-based health care.

dave
Premium,MVM
join:2000-05-04
not in ohio
kudos:8
Reviews:
·Verizon FiOS
said by DKS:

Let Windows 7 do its thing and the rest of us should be fine.

There's no alignment issue with Windows 7 - it knows how to do the alignment.

Previous versions of Windows did not; so those are the systems on which you need to fix the alignment (if you care). That includes the update from not-Win7 to Win7 case, of course.


digitalfutur
Sees More Than Shown
Premium
join:2000-07-15
BurlingtonON
kudos:2
reply to DKS
Agreed. Even defragging sata drives is required only rarely (once or twice every 6 months).

Super fast CPUs and HDDs render the performance penalty of fragmentation as close to 0 as a mechanical device can be.

Sometimes ya just gotta let go...
--
Logic requires one to deal with decisions that one's ego will not permit.
All that is necessary for the triumph of evil is that good men do nothing - Edmund Burke.


DarkLogix
Texan and Proud
Premium
join:2008-10-23
Baytown, TX
kudos:3
reply to dave
said by dave:

said by DKS:

Let Windows 7 do its thing and the rest of us should be fine.

There's no alignment issue with Windows 7 - it knows how to do the alignment.

Previous versions of Windows did not; so those are the systems on which you need to fix the alignment (if you care). That includes the update from not-Win7 to Win7 case, of course.

If in doubt check the alignment, its a few command line commands and you can see if its aligned.

if its not then fix
this applies to all SSD's and all 4k block drives (often called advanced format, as the 4k block size was needed to make drives over 2TB)