SSD - Is 60GB=64GB, 120GB=128GB & Is Windows RAID better/worse than controller RAID

Posted on 2012-03-16
Medium Priority
Last Modified: 2012-03-26
I have a 64 GB SATA III SSD in my home desktop PC (see bottom for specs) with Windows7 enterprise installed.  I have the OS and programs stored on the SSD and all my data on a second 2TB HDD, however due to Microsoft/Adobe updates, I now have only 4GB left on the drive and was planning on expanding the drive by buying either 1 more SSD and doing RAID0 or 2 more SSDs and doing RAID5. First, before you all try to convince me never to do RAID0, since I store all my data on a second drive (and even changed the user profile folder to be the root of that drive) and plan on imaging the SSD drive after all programs are installed, I could care less if I lost all data on the SSD drive array. But I do have two sets of questions:

1. I have read about the garbage collection problem and lack of TRIM support on hardware raid controllers, but is this an issue with Windows volume management software RAID?  Will performance significantly improve with controller RAID?  Will drive life significantly improve with TRIM/garbage collection support if available in software RAID?  This will answer if controller or software RAID better with SSD.

2.  I see "60GB" and "64GB" drives and was wondering if these are the same real capacity with different labels, or actually different capacity, especially if doing a RAID5 set up where this matters more.  I searched and searched but did not find evidence of this one way or the other, the best I can tell is that write amplification over provisioning may have something to do with different labeling of drive capacity, but can anyone provide proof of whether a "60GB" SSD drive is equal or not to a "64GB" SSD drive, and would I loose capacity if I mixed them in a RAID array?

Crucial CTFDDAC064MAG-1G1 RealSSD C300 2.5" Solid State Drive
AMD Six Core 4.0GHz Overclocked Barebone PC - ASUS M4A89GTD PRO/USB3
Question by:lefton4ya
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Accepted Solution

David earned 900 total points
ID: 37731288
Windows7 handles TRIM fine. Unless you pay much more than the cost of your PC for one of the high-end LSI RAID controllers with embedded SSD support (and you have to buy their SSDS), ... then this is the only game in town for you.

Here is a good article ..

Now excuse me because I WILL get on the soapbox.  

You are throwing money away.  You buy a SSD for IOPS not THROUGHPUT.  If you want throughput you can get a lot more throughput for a heck of a lot less money by purchasing 3 mechanical disks and putting them in RAID0.

(You also can't boot RAID5 on SSD with MSFT software RAID), unless you waste space and split disks so that 2 of them have a mirrored RAID1, at the beginning of the disks, and then all the disks have the same sized RAID5.  (So empty space at beginning of all but 2 disks).

This means I/O load will differ.
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Expert Comment

ID: 37731361
A single SATA 6Gbit/sec SSD will provide more than enough performance for most people.  Unless you are running benchmarks or a heavy duty database, installing SSDs in a RAID0 setup will not be distinguishable from a single SSD setup.

The capacity of these drives depends a lot on what the manufacturer decides to reserve for over provisioning.  The NAND chips come in standard sizes, so theoretically, all drives with the same number of specific capacity chips should have the same storage.  The amount you lose in a RAID setup will depend on how much the internal SSD controller reveals to the outside world.
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Expert Comment

ID: 37732794
Here's a little trick to free up a couple of gigs of disk in case you are interested.

Page file settings,if you have more than 4 gigs of memory,you probably don't need one (or a very much smaller one of say 2 gigs or less.")

IE if you have say 8 or 16 gigs of memory and the file is Windows managed,it will reserve 8 or 16 gigs of disk space on the boot drive.

If you need a swap file,just move it over to the cheap disk and 0 it out for the SSD.

You can also remove the spack backup files and free up another half gig.

That's an easy way to free up 10 or 11 gigs on your SSD.
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Author Comment

ID: 37745175
RAIDing SSD can get you throughput though, as this video proves: Samsung SSD Awesomeness.  I guess I mostly want all my programs to START fast but also do photo and video editing and found programs themselves RUN a whole lot faster when they are installed on the SSD, especially the adobe programs (I can not fit the 25+ GB CS5 production suite install on it, only the 10 GB CS5 design studio).  As for pgm554's tips, I had already disabled swap file (with my 8GB of memory) and cleaned out SoftwareDistribution\Download and the temp file folder, but figuring out how to remove windows backups in Winsxs and adobe update backups is a probably good idea for me to clean up more space, and I realized the hibernation file eats 3-6 GB (depending on mem usage). I though adding another 64GB SSD to add more space was cheaper than buying a 128GB SSD, and figured i might as well raid it.

Thanks dlethe for letting me know that RAID5 SSDs will not boot without really expensive hardware or wasted space, so I guess I will stick with RAID 0.

I still do not have a definitive answer if drives packaged as "60GB are the same real capacity (combined NAND chip size) as those labeled "64GB"  For instance, is the OCZ Synapse Cache SYN-25SAT3-64G equal in capacity to OCZ Vertex 3 VTX3-25SAT3-60G (even though I know other specs are different, both have SandForce SF-2281 controllers)
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Assisted Solution

pgm554 earned 600 total points
ID: 37745291
I've done the spack cleanup and got about 3 gigs of disk,so it does work.


You could try the new cache only SSD's for about a hundred bucks and maybe use WD 10k SATA drives as they are pretty fast and are cheaper than SAS or SSD


Author Comment

ID: 37753043
Thanks again for the tips.  I cleaned about 5 GB of space from WinSxS which leaves me with about 10 GB left, but I really want to install all my programs on it (Adobe Production Suite uses 16+ GB).  The caching SSD looks interesting, but since I already have a 64GB SSD, I think I am going to by another one and RAID0 them using Windows RAID.  My question still remains, is it OK to RAID a "60GB" drive and a "64GB drive".  My guess is yes and the worse that happens is I loose 4GB of data.
LVL 47

Assisted Solution

David earned 900 total points
ID: 37753096
RAID0 doesn't care about having same number of blocks, or even if the entire disk is used in RAID0.  With host-based RAID, you can even use part of a device in RAID1, and another part in RAID0.

I haven't tried mixing & matching RAID0 & RAID1 on Win7 as boot device, but it will probably work.

That might be a good way to go anyway,  Allocate a equal-sized partition in each SSD starting at block0 to be a mirrored RAID1 for booting, and most important files,  then make a large RAID0 for the rest.

Then you get best of both worlds, data protection where you need it, and convenience of a larger device where you don't

Author Closing Comment

ID: 37768709
I decided to just clean up space on my SSD for now.  I realized you cannot BOOT windows7 to software RAID0, and my (and most other) RAID controller does not support TRIM/garbage collection, so it is not really worth RAIDing for me.  I may purchase a 128GB SSD or one of those caching SSDs in the future.

I still don't have an good answer if an SSD labeled "60GB" is equal to one labeled "64GB" and one labeled "120GB" is equal to one labeled "128GB"?

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