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I have a computer with RAID1 SSDs, but the performance I'm getting out of them is really bad (around 20MB/sec sequential read). They don't have TRIM enabled since it's an old Linux kernel, so before I upgrade just to turn on TRIM, I want to ensure that I'm solving the right problem.

Is there a way to definitively prove that TRIM is my problem with my disk performance?

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Super User is for computer enthusiasts and power users. questions about …computer hardware, computer software, personal and home computer networking. Your question doesn't fall into any of those catagories. –  wizlog Feb 17 '12 at 19:24
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While it may be a server, this is computer hardware, so I do not believe it is completely off topic. –  music2myear Feb 17 '12 at 19:37
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Analyzing hard drive performance seems squarely on topic to me. –  mlissner Feb 17 '12 at 20:00
    
Check also for firmware updates. Some SSD devices had serious bugs with early firmware versions. –  jap1968 Feb 21 '12 at 8:42

3 Answers 3

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If you get a very recent release of e2fsprogs, you can run e2fsck -f -E discard to check the fs and issue discards on all of the free space. Note that it is write performance, not read, that generally degrades on an SSD that isn't trimmed. Doing a trim now or upgrading to a new kernel and enabling auto trim may improve things over time, or at least keep them from getting worse, but your best bet is to backup the whole system, then wipe the entire ssd with hdparm's security erase command, then restore.

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Doing a wipe and restore is the LAST option, but good to know about the write vs. read performance. Since both are affected, I'm pretty sure this something bigger. –  mlissner Feb 21 '12 at 6:45
    
I'd stay away from the discard support in e2fsck for a while yet as it still seems to be buggy. –  psusi Feb 21 '12 at 14:51

You could try to boot with a live system having a kernel able to apply the TRIM command to the disk.

This way you could improve your disk performance without having to change the kernel of your system.

Unfortunately, I do not know which is the minimum kernel version that you need.

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According to Wikipedia, it's 2.6.33. Wild that I could run a HD-fixing kernel on a disk without installing that kernel. I'll consider this as a last option, before wiping, but I think it looks like this isn't a TRIM issue at all. –  mlissner Feb 21 '12 at 6:48
    
Simply booting from the livecd won't do anything. You would have to delete and recreate all of the files with kernel discard enabled since it only issues the discards when you delete files. –  psusi Feb 21 '12 at 14:54

soft RAID1 does not pass TRIM command, even less RAID controllers....

It could happen your SSD drives are 10MB/S, just that seek time is 0.0000s

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I sure hope not - it's a server. My desktop gets 10X that speed. –  mlissner Feb 18 '12 at 5:22
    
Does your desktop use same RAID controller? –  ZaB Feb 18 '12 at 9:58
    
Nope. It's software RAID. –  mlissner Feb 21 '12 at 6:46
    
Problem lies in RAID controller. you do not control what it does on disk interface. Move to soft raid (also available in JBOD and AHCI modes if RAID controller provides them) and see how well it does. –  ZaB Feb 21 '12 at 21:31

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