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2011-10-20, 15:06 #1
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Any special steps needed before overwriting an entire SSD with an image?
(I originally posted this question in Crucial’s SSD forum. I think any SSD owner might benefit from it so I’m posting it here.)
My goal is to restore a full Windows 7 installation (complete with Office 2010, etc.) to an SSD from an image file. That means the imaging program is going to write a bunch of data all at once to the SSD. I don’t think any currently available imaging programs reset the SSD’s NAND before doing this, so it would seem that an MLC SSD needs some prepping to receive this data blast.
(I’ve read that an MLC SSD is like a DVD re-writeable disk: it needs a special erasing step before it can be overwritten. True? Heck I don’t know. But the manufacturers leave it to us to weed through all the contradictory advice in forums so that’s what I’m trying to do.)
The Weed Patch
OCZ officially recommends you use their Secure Erase tool that’s designed to reset the NAND to factory state. I assume OCZ’s Secure Erase tool resets the NAND with a single magical command to the “charge pump”.
Crucial says this isn’t necessary, that instead you can use several different approaches to delete all the partitions – or delete the entire volume – from the SSD. Then, with the SSD still connected to a Windows 7 system let GC and TRIM clean it up.
Read this post at StorageReview.com for an authoritative-sounding explanation of what garbage collection (GC) and TRIM do. It (and other articles) left me with the impression that TRIM imposes wear on the SSD. Plus, you need a working W7 PC to do what Crucial recommends. And there remains the question of how long it takes for GC and TRIM to do their work.
Anand wrote in an article about SSDs: "Formatting/deleting everything on the drive won’t work because those pages on the drive will remain full of data." He then proceeded to recommend using HDDERASE, but that was in the context of returning an SSD to optimal performance. I have to assume that since he wrote that in 2009 TRIM and GC weren’t available or as developed to the extent they are now. Still, his article adds credibility to using HDDERASE or a similar secure erasing program.
But what tool? It’s easy to know with OCZ because they offer their own "secure erase tool" but how about other SSDs?
I have the impression that not all secure erasing programs are appropriate for SSDs. For one thing, using the term “Secure Erase” causes confusion. “Secure erasing” has long been used to describe programs that write various patterns to HDDs – sometimes multiple times -- to erase every last vestige of user data on a magnetic medium. As one person replied in Crucial’s forum, some write 0’s and some write 11, which he believes is the native state of every cell in an SSD. Regardless of the pattern, it all still involves “writing” to the SSD’s cells, doesn't it? Sounds to me like more wear on the SSD, and time wasted.
So maybe the Center for Magnetic Recording Research’s HDDERASE is the best tool to use when one isn’t available from the SSD manufacturer, though there’s that word “magnetic” again and SSDs are far from magnetic technology. Moreover, SSDs are never mentioned in the HDDERASE section at CMRR's site or in HDDERASE’s docs.
Feeling a little hesitant about using HDDERASE I searched for “HDDERASE” and “SSD”, which lead me to the following recipe by an individual in OCZ’s forum, of all places. It’s just detailed enough to sound official, plus, I found basically the same steps at several other sites):
(3) Enter BIOS
(a) Set Storage to IDE + Compatible
(b) Set USB Legacy to Enabled
(c) Disconnect ALL SATA drives + Externals
(4) Reboot and F8 to boot USB (i.e., to boot the HDDERASE media)
(a) Re-connect boot drive ONLY (drive to be imaged) to SATA port # 1 when at DOS prompt
(5) Load HDDERASE.EXE and execute
This post was followed by a reply that said: "Your guide has work 100%. thanks man, How long does HHDerase take? It was over in less then 2 seconds. (sic) "
The recipe sounds conclusive, yet I found other forum posts saying that HDDERASE doesn't support SSDs, or "version HDDerase 3.3 works with SSDs but not version 4." (Why must I weed through all this!?)
The recipe also isn’t as simple as “just run HDDERASE (no command line options or other actions needed).”
Come on, Crucial et al. Stop the need to weed. What you and all other SSD manufactures should do, IMHO, is publish a definitive explanation of what to do before writing an image to a used SSD. This is a very common operation with HDDs so it's not an obscure question. And you all gotta agree on it. Preclude debate and continued speculation in forums by addressing why other methods aren’t as good. Surely there’s one best answer that all SSD makers can agree upon.
2011-10-21, 09:53 #2
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A low level format should be more than suficient. But if a specific manufacture offers advice on their own hardware, go with it.
the SSD HDD controler should be set to AHCI, not IDE.
You could take you os disk, boot with it and do a low level format. No need for anything else.
Even an image will over write to the SSD without issue.
2011-10-21, 12:15 #3
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You should never low level format a modern hard disk. The disk is self managing and anything apart from a straight format is asking for trouble.
SSDs are different in that you ideally want to re-initialize the storage before re-imaging, but if the manufacturers are not advising how to do this it most likely means there is no user accessible method. I don't think it will make a great deal of difference anyway given the performance of an SSD.