Raid 0, x-25m g2, and performance

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gweminence

Limp Gawd
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Dec 22, 2006
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So, I just bought my second intel x25m g2 SSD, and am considering raid 0'n them. I've done some research, and it seems that:

1. Trim does NOT work in raid 0 -- (I know this is true)
2. The best thing to do is to leave more than the base free space as unformatted. For example, make the raid size 120gb, instead of the (ostensibly) 160 they'd afford. Is this accurate? The reason I'm not clear on this is because it seems like some people put stock in the intel ssd toolbox trim-like function that can be run manually, and will keep the drives going good. Is this true? If so, does this mean that I can utilize the entire 160gb of the raid volume?

Thanks in advance for any replies. I did my research, I just would like this little bit of clarification. Thanks!
 
Yes you should reserve space dedicated to the SSD as spare area; by creating a smaller partition and leaving the rest unused.

However, since one of your SSDs is used, you would need to Secure Erase that one before RAIDing them. Otherwise, part of the storage space reserved on that disk would not be used by the SSD; wasted space. The SSDs has to be brand new for the space reservation to work. A Secure Erase would work in doing just that.

If you leave 20-25% space unused, in addition to the default 6,8%, then you should have enough spare space to fight performance degradation over time, and get a healthy benefit from RAID0-ing them.

Good luck!

Oh and make sure your partition is aligned; check with AS SSD and it should say something like "1024K - OK" and not "31.5K - BAD".
 
Sub.mesa, thanks for your reply. Any thoughts regarding the intel SSD toolbox functionality that performs 'manual' trim? Would that allow me to use the space?
 
I'm not really sure how the Intel Toolbox works; it might be writing zeroes or ones interpreted by the SSD as being 'holes' in storage space; just like ZFS considers zeroes to be holes in the ZFS filespace. That way it would have the same effect as TRIM, but at the cost of actual write cycles; while TRIM does not cost any write cycles.

Therefore, I recommend to increase the default 6,8% spare area on Intels to about 20-25% especially if you do not have TRIM. That way you dedicate space to the SSD and fight erase block fragmentation.

So it is a balance between storage capacity, write endurance and performance.
 
One last point of clarification. The 25-30% that I leave 'unused' should simply be, unused volume (ie not formatted and therefore not it's own partition), or, it's own partition, and just nothing installed upon it? Or does it matter?
 
Just unpartitioned would work best. Actually all space is spare space; until you write to it. It will stay 'claimed by the OS' until either it receives a TRIM command for that spot or a secure erase. So not partitioning the last chunk would simply cause nothing to be written to that location, which achieves the desired effect.
 
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