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Apple Seeds Mac OS X 10.6.7 Build 10J869 to Developers
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USB tethering is supported in Canada on Rogers wireless network since 2009 on non jailbroken iPhones yet crashes a Mac every time.
MrNomNoms said:
USB tethering is supported in Canada on Rogers wireless network since 2009 on non jailbroken iPhones yet crashes a Mac every time.
I had a similar problem moving my RAID-0 setup from my 2010 MBP to my new 2011 MBP. I ended up
(1) cloning the RAID to a single drive
(2) upgrading that clone to Mac OS X 10.6.6 (10J3210) with the disk that came with my 2011 MBP
(3) booting off it
(4) cloning it back onto RAID-0 in an enclosure Elite-Al Pro Dual mini
(5) re-installing the RAID-0 stack back into my 2011 MBP
(6) Runs like a champ!
see
Why not until? TRIM works as well with disks in an already used state as with new disks. No need to wait for TRIM...
Not quite true.
TRIM works as part of the filesystem deleting a file - the filesystem sends an extra ATA command (or several) to the drive to notify the drive that some sectors have been freed.
When you upgrade the OS to one with TRIM support - you need to insure that something tells the drive which sectors are free.
This can be a filesystem or drive utility that walks the free space list, sending TRIM commands to the drive for each extent of free space found. It can also be done by a simple utility to create a huge file that uses all free space, then by deleting the file.
After a few months of use, there probably would be no significant difference between doing nothing and using a utility to force TRIM to happen.
Why? You certainly can tell the system where the stale blocks are so TRIM can take care of them, can't you? I don't quite understand, obviously.
Why? You certainly can tell the system where the stale blocks are so TRIM can take care of them, can't you? I don't quite understand, obviously.
Let me try to explain it a little better. Please bear with a long-winded explanation I hope will be generally helpful to people trying to understand TRIM.
As you probably know, a key factor in SSD write performance is that the SSD needs to have a nice pool of pre-erased pages available. Blocks are usually 256 KiB or 512 KiB, and contain many (usually 4 KiB) pages that that contain actual data. A page can only be written once after each erasure, and erasures can only occur for an entire block - any block that has a valid page cannot be erased and reused.
When the drive runs low on pre-erased pages, garbage collection will take an erased block, look through used blocks and move any valid pages in the used block to the pre-erased block, and when all valid pages have been moved from the used block erase the used block. Repeat until the new block is filled with valid pages (and/or the needed number of blocks have been freed and erased).
If you do a write, and no pre-erased free pages are available, you have to wait for the drive to copy pages and erase a block.
Unfortunately, (without TRIM), when a file is deleted the drive has no way of knowing that its pages are now free. The drive has to deduce which pages might be free (for example - if you rewrite a page, the drive writes the new page and can deduce that the old page is now free).
The TRIM feature is a simple command that lets the operating system (the filesystem) inform the drive that a range of pages no longer has valid data. When you delete a file, that file's extents are TRIMmed. If you format a drive, the entire partition is TRIMmed.
This means that space reclamation can be tied to file deletion, not to page re-use. The drive can pre-erase more blocks, and be ready for writes much faster.
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Anyway, back to the post's question of:
The issue that I didn't explain clearly is that if you simply upgrade to an OS with TRIM support - nothing happens with all of the deleted data. The drive still maintains that data even though there is no filesystem reference to it.
Nobody will "tell the system where the stale blocks are" without someone making it happen.
Ideally, the OS upgrade that added TRIM support would automatically run a filesystem-aware disk utility on all TRIM-enabled SSDs. This utility would walk the filesystem and send a TRIM command for each free extent on the volume.
Not quite as good would be to update the disk utilities to make such a process a manual task.
Third, would be a simple utility that creates a file that fills free space, then deletes the file. (Since the TRIM-enabled filesystem will notifiy the disk of all the extents freed by the delete.)
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And finally, even if you do none of the above other than upgrade to a TRIM-aware OS, as you write, overwrite and delete files the drive will see the pool of TRIMed blocks and pages grow. A few months after the upgrade, your performance will be essentially equal to what you would have seen in the perfect case of the OS upgrade running a disk utility to trim all free space during the upgrade.
This is because once you have a few percent of the disk space pre-erased and available - you'll run full speed on most realistic applications. You won't be able to measure the difference between having 5%, 10% or 50% of the disk pre-erased.
There's a good, more technical (but not overly so) description of the issues at http://en.wikipedia.org/wiki/Write_amplification.
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Thanks Aiden!
So if you do one of the mentioned three points, your SSD should be correctly trimmed and deleted data isn't being maintained by the system anymore, right?
Still don't see the advantage of using an all new disk instead of an already used one except that someone has to make the magic happen. If Mac OS is not doing it automatically, there certainly will be tools to do that. I wouldn't mind to do that myself.
So if you do one of the mentioned three points, your SSD should be correctly trimmed and deleted data isn't being maintained by the system anymore, right?
Still don't see the advantage of using an all new disk instead of an already used one except that someone has to make the magic happen. If Mac OS is not doing it automatically, there certainly will be tools to do that. I wouldn't mind to do that myself.
"Maintained by the SSD", not "maintained by the system". But yes, if the OS and drive support TRIM then any of the three steps should result in the drive being aware of which pages are unused, and allowing it to pre-erase large numbers of blocks almost immediately. The point of TRIM is to allow the drive to pre-erase blocks without unnecessarily copying unused (but dirty) pages from a partially used block.
Right, I see little point in a new disk. If the old one supports TRIM, a disk utility will quickly clean it up and TRIM free space.
Even in the absence of any disk utility, a TRIM-enabled OS will understand file deletions and TRIM the extents. If you just copy a bunch of ISO files to the disk, then delete them, you'll have virtually all of the benefits of the best TRIM utility available. If you copy and delete 5% of the disk space, you'll have enough pre-erased blocks to run at full speed.
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BTW, another tip for using an SSD with any OS (TRIM-enabled or not) is to under-provision the drive - so that the extra space adds to the "over-provisioning" of the drive. The "wasted" space increases the pool of pre-erased blocks and improves the performance and life-span of the drive.
For example, drives usually include some over-provisioned space. Since SSDs are built from flash chips, they'll have a capacity of a binary multiple - for example 128 GiB (137.44 GB). If the drive is sold as a 128 GB drive, then 9.44 GB is "hidden" for pre-erased blocks and wear-leveling. It's common that 128 GiB drives are sold as 120 GB drives, so that 17.44 GB is "hidden" for wear-leveling and performance.
If you don't have TRIM, it's recommended in many situations that you should make smaller partitions on the drive, for example a 100 GiB partition on a 120 GB drive, to leave more space for over-provisioning.
(If you have TRIM, there's only a very minor potential advantage to under-provisioning. If the partition has 50 GB of free space, that's available for wear-leveling and performance anyway because of TRIM - regardless of un-partitioned space on the drive.)
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Ye you're right of course, that's what I meant.
That's exactly what I wanted to hear. I'm relieved now that I don't have to secure erase my MBA 2010 SSD before I'm going to install Lion eventually in Summer.
Finally got around to install 10J869, and I think it somehow made the whole user experience faster. I can't put my finger on it, but it is faster...
Perhaps they did something with the Graphibcs driver (I have the ATi HD 4870 in my Pro), or it has to do withthe SSD handling (I am using a 256GB C300).
Anyways, it feels faster, and no issues whatsoever
KB
Perhaps they did something with the Graphibcs driver (I have the ATi HD 4870 in my Pro), or it has to do withthe SSD handling (I am using a 256GB C300).
Anyways, it feels faster, and no issues whatsoever
KB