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On Mon, Jul 9, 2012 at 10:26 AM, Jarry <mr.jarry@×××××.com> wrote: |
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> Hi, |
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> |
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> I'm building small server for VPS-hosting purpose (not decided |
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> yet, probably KVM or ESXi). Althought it is "non production", |
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> reliability is still issue for me. I'm considering using two |
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> small SSD (ie. Intel 313, 24GB, SLC) in hw-raid1 (Adaptec 3805) |
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> just for hypervisor, and 2xHDD/raid1 for VPS. |
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> |
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> I started looking for info on internet but results are not |
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> conclusive. Opinions vary from "no problem, use SSD&raid1" |
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> to "using SSD in raid is not recommended no matter if it is |
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> SW or HW". Mostly missing trim-command is mentioned as reason |
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> for not using SSD in any raid. |
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> |
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> Does anyone have any experience with SSD in raid (SW or HW)? |
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> Is it safe to use it on server? |
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> |
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> Jarry |
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|
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On the surface it doesn't make a lot of sense to me. If you have two |
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drives mapped against each other in a RAID-1, and then you TRIM part |
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of 1 drive but don't TRIM the same part of the 2nd drive, it seems to |
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me that you're discarding part of your redundancy, aren't you? What |
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would mdadm itself (or anything else) know about remapping that stuff? |
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Granted, mdadm could be informed and probably reconstruct the RAID-1 |
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in a new location, but as you TRIM out different parts of each SSD |
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it's going to get messy I think. |
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|
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If you look up TRIM in Wikipedia there's a little bit of info |
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suggesting some support for some file systems. |
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|
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http://en.wikipedia.org/wiki/TRIM |
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|
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I can say from reading the mdadm list for the last year that it's a |
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conversation that doesn't come up all that often and mostly goes away |
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pretty fast most of the time there. Check their archives. |
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|
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In my case I'm running a small server here that's currently running 3 |
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VMs which is typical for my work day. I'm considering adding a single |
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SSD to the system to host the VMs but using rsync to back them up to |
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HDD RAID each evening. |
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|
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HTH, |
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Mark |