Best way (only?) to setup SSD's for using TRIM

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

I've got two new SSD's that I want to set up as RAID1 and use strictly for the OS and MySQL DB's partitioned accordingly.

I'll be using the 3.4.6 kernel for now in openSuSE 12.2 with ext4. So after a lot of Google'n and reading it is my understanding that discard is not sent to the devices via the raid drivers. I am aware of Shaohua Li's patches to make it work but am not inclined to use them due to openSuSE's Online Update replacing the kernel. I'm not against patching and gen'ing a kernel, that used to be SOP, but just don't want deal with that overhead. Of course unless I really need to.

So I've read, and if I understand things correctly, I can use LVM and RAID1 and the the discard commands will be sent to the devices. Is that correct and currently the only way or is/are there other ways?

I've also read that a lot of people are saying TRIM isn't needed because the SSD's garbage collection is so good now TRIM isn't needed. But I don't see how that could work because the SSD's don't have access to the file system so they don't know which pages in the blocks are marked unused to do any consolidation and erasing. And using TRIM is suggested in a OCZ document I read and who's drives these are. Unless, the SDD when it has to change a page moves the whole block then erases the old block? But without TRIM in could be moving invalid data too because it doesn't know that and that to me sure doesn't sound efficient and this operation would be a perfect time to get rid of the invalid data if it did know.

And due to PEC I'm wondering if this is even a good idea? Granted the OS files can be considered somewhat static, with the exception of /var/log so maybe that shouldn't go on the SSD, and maybe MySQL shouldn't either because for things like ZoneMinder it's DB is pretty dynamic. But with all the logging going on, and there is a lot, and the dynamic nature of the MySQL data is the exact reason I want it put it on SSD's, for the speed. See my quandary?

This is my best understanding of things right now so I came here to and am asking the experts for help in clarifying and understanding this and pick the best direction to go. Have the SSD's for a couple of weeks now but holding off using them until the I can determine the best way to use them. Oh and the SSD's are OCZ Vertex 4 VTX4-25SAT3-256G.

To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at

[ATA RAID]     [Linux SCSI Target Infrastructure]     [Managing RAID on Linux]     [Linux IDE]     [Linux SCSI]     [Linux Hams]     [Device-Mapper]     [Kernel]     [Linux Books]     [Linux Admin]     [Linux Net]     [GFS]     [RPM]     [git]     [Photos]     [Yosemite Photos]     [Yosemite News]     [AMD 64]     [Linux Networking]

Add to Google Powered by Linux