Have you looked for information?
It is not just benchmarks. Meaningless when any SSD will saturate the bus.
Reliability, TRIM Enabler, the design (controller, firmware, etc)
Larger SSDs cost so much more, have more I/O channels.
A 10K WD VR is a solid 180MB/sec $104 250GB too.
We have threads every day. I'll leave it to you to google and find those.
SSDs are so much faster than rotating drives it is hard to make a mistake in performance.
Anyone running an SSD needs to do something about "deleted" data. Mac OS X simply adds those blocks to the free pool, and does not clear them. This forces the SSD to continue to carry and replicate them as part of its much larger "superblocks", as if they were still valid. The drive can fill with blocks full of deleted data that can wreck performance and even cause premature drive failure.
One can periodically consolidate free space and immediately Zero the free space, but TRIM Enabler from groths makes a simple patch to enable TRIM for non-Apple SSDs.
Apple has not tested this with third-party SSDs, and does not endorse it. I have been running it trouble-free, but your mileage may vary. There are other TRIM solutions as well.
If you enable TRIM and then run Disk Utility ( Repair Disk ), an additional line appears in the ouput: TRIM-ing unused blocks (or similar). It is very satisfying. The drive is notified and marks those blocks as surplus, and when the drive controller gets around to its garbage collection, those blocks can be eliminated.
Creating a slightly smaller partition than the maximum gives the drive additional over-provisioning (extra free blocks) that can enhance drive operation in the long run.
Grant Bennet-Alder wrote:
...If you enable TRIM and then run Disk Utility ( Repair Disk ), an additional line appears in the ouput: TRIM-ing unused blocks (or similar). It is very satisfying. The drive is notified and marks those blocks as surplus, and when the drive controller gets around to its garbage collection, those blocks can be eliminated...
That would also be an indicator that TRIM is actually functioning. It's caught my attention first because OWC maintains that SandForce controllers don't get along well with TRIM and second because my SSD is a RAID configuration and isn't supposed to be compatible, SandForce or not.
Assuming that TRIM is non-destructive if it doesn't work with a particular configuration, the Disk Utility tip would be a good way of seeing what's actually going on.
Thanks for your input. Discussions can be more productive if we all try to be more diplomatic.
Most operating Systems, Mac OS X included, simply add the actual data blocks from deleted files to their Free Pool, and do not notify the drive controller that the data blocks are no longer needed. The free pool is maintained by Mac OS X as a bitmap, so whether these blocks will be re-used soon depends on the new-file allocation algorithm, which I believe at this writing is still "first fit".
In the normal course of business, these data blocks are not over-written automatically. This is what allows third-party "deleted File Rescue" programs to recover some of your files after you nominally deleted them. This is also why it is a prudent practice to overwrite your drive before selling it.
For rotating drives whose minimum Allocation Block is the same or larger than a physical data block (0.5K or 4K depending on the drive), this presents no problem in daily use, as the next write will overwrite entire blocks of un-needed data.
SSDs tend to use extremely large Blocks internally. Instead of replacing a 4K block, they need to read, erase, and rewrite Huge blocks. When the controller has not been notified of what Mac OS X considers "deleted" or "un-needed" data, that data must be carried along and replicated into the re-written block. This means the SSD drive controller carries many partially-written blocks that contain some "un-needed" data. Free space could be consolidated into larger empty blocks (with much faster write times) if only the drive controller knew which blocks were un-needed.
TRIM provides that notification and can allow the SSD to deal with the "un-needed" data. Under SATA II, the commands are for immediate execution, so the drive can at most mark the blocks as surplus for later freeing. Under SATA III, the TRIM commands can be queued, so they can be executed out-of-order. That would allow them to be done sooner, at the end of a burst of activity.
These drives are just a small circuit card internally. I removed an early one I bought from its sheet metal can and the connector was as big as the rest of the circuitry.
Most of these are set up to be 2.5" form factor drives. If you buy a 3.5" form factor, it is a specialty item, and you sharply limits your choices.
If you install it in a regular drive bay on a sled, you will need either:
a) an adapter/sled that maintains the correct spacing (such as this one sold by OWC/MacSales for the 2009 model MacPro)
b) an Icy Dock or equivalent sub-enclosure with a connector and a short cable
c) a 2.5 plus 3.5 combination sled for your series of Mac Pro. 2009 and later are different from 2008 and previous, such as these for US$29:
Alternatively, since there is no vibration, you can install it in a 2009 and later in the lower Optical Drive bay, or in a 2008 and earlier if you wire up the SATA ODD ports from the motherboard and fish the SATA cable(s) up to the optical bays. No mounting is required, but you could Velcro it in place if you prefer.
Most operating Systems, Mac OS X included, simply add the actual data blocks from deleted files to their Free Pool, and do not notify the drive controller that the data blocks are no longer needed.
That is false information.
Instructions are sent to ALL storage devices when data is deleted in the OS, otherwise the data would appear intact if connected to a different machine. The SSD controller is instructed to remove the data from the directory and its programming understands that such command means it can clear the blocks for use when it has unused processing/data cycles.
In the normal course of business, these data blocks are not over-written automatically. This is what allows third-party "deleted File Rescue" programs to recover some of your files after you nominally deleted them.
That is false information.
Data is written progressively to a drive from outer track to inner (in a hard drive) and oldest cleared to youngest (in an SSD, called "wear leveling"). That means when you delete a file in a hard drive, that space will be first to get written over and first cleared to be ready to write in an SSD.
Thats why older Windows OS' like 95, 98 and XP had such fragmenting issues which drove defragmenting to become a regular practice until Vista.
TRIM provides that notification and can allow the SSD to deal with the "un-needed" data.
TRiM is obsolete. Modern SSDs have Garbage Collection internally, independent of the OS. That is why Sandforce controllers have issues with TRIM.
These drives are just a small circuit card internally
You don't understand what SoC (system on chip) is?
I removed an early one
Technology progresses very rapidly. Today's SSDs are significantly different and smarter in controllers, memory cells and programming than those of even three years ago.
or in a 2008 and earlier if you wire up the SATA ODD ports from the motherboard
The ODD connectors are only present in 2006 models. The 2008 revision eliminated installation of the connectors. Per Apple.
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A bit less righteousness on your part could lead to a more productive discussion. There may yet be something to be learned form hearing other people's opinions rather than attempting to squash them.
otherwise the data would appear intact if connected to a different machine.
The directory entry IS cleared. The directory entry is unrecoverable. The filename will usually be lost.
The actual drive extents (where the data blocks from the file are stored) are NOT routinely cleared, unless you choose "Secure Empty Trash" or use a similar method.
There is no need to move the drive to another computer. The data blocks of accidentally-deleted files CAN be recovered through third-party Utilities. Norton Utilities, Tech Tool Pro, and Data Rescue all perform this trick daily.
Data is written progressively to a drive from outer track to inner (in a hard drive) and oldest cleared to youngest
That would be true if data were never deleted. But as I mentioned above, in Mac OS X the algorithm used is "first fit". Starting from the lowest logical block number, the first available contiguous space large enough to accommodate the requested size is the space used.
The free pool is maintained as s bitmap. A one-bit for every allocation block that is available ("never used" OR deleted). From that bitmap data structure, simple routines quickly determine the lowest-numbered contiguous region where the file will fit, and that is what is allocated. Then the Directory entry is created.
In rotating Hard Drives, there is no general re-mapping of logical block numbers to different regions within the drive. And unless files are rewritten, there is no migration or gratuitous movement of files unless they are deliberately re-written by a program or found to be both large and fragmented.
and oldest cleared to youngest
This simply does not happen in rotating drives, unless Mac OS X finds the files are both large and badly fragmented.