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Am 09.07.2012 19:26, schrieb Jarry: |
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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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I don't think trim is currently supported in mdaid. AFAIK dmraid |
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supports it as long as the RAID controller plays along. I'm unsure about |
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LVM mirrors. |
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|
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But trim is not your only issue: mdraid and LVM as well as most (all?) |
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hardware RAIDs will mirror all blocks from one disk to the other when |
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you assemble the RAID-1. This means that all blocks on your second SSD |
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will immediately be marked dirty which incurs a significant performance |
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penalty. |
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|
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My advice: Use the second disk to do incremental snapshots of the other |
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on the filesystem level. Or, if you feel lucky, use btrfs's mirroring |
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capabilities. |
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|
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Regards, |
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Florian Philipp |
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