hdd + ssd
Hello I'm trying to understand why and how to add one or more SSD (as a cache drive / keeping xfs log) to a traditional spinning xfs storage volume.
I mean: which data will go to the ssd ? Inodes and dentries will go to the ssd ?
Will the _read_ performance increase ?
In general I'm looking to increase (cache) the reading performance of folders with a lot of small files (emails), for email servers.
Feel free to let me rtfm :)
I'd gladly study the documentation / articles / benchmarks but my google-fu isn't in best shape.
Thank you,
Mike
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Quoted 4 lines · On 10/22/15 1:23 PM, [email protected] wrote:
Hello I'm trying to understand why and how to add one or more SSD (as a cache drive / keeping xfs log) to a traditional spinning xfs storage volume.
I mean: which data will go to the ssd ? Inodes and dentries will go to the ssd ?
Will the _read_ performance increase ?
You might want to look into something like dm-cache
https://en.wikipedia.org/wiki/Dm-cache
(TBH, I've not used it before, so grains of salt apply for your usecase).
Putting the log on an ssd is not likely to be the solution you want; it certainly won't speed up reads.
-Eric
Quoted 6 lines
In general I'm looking to increase (cache) the reading performance of folders with a lot of small files (emails), for email servers.
Feel free to let me rtfm :)
I'd gladly study the documentation / articles / benchmarks but my google-fu isn't in best shape.
Quoted 7 lines
Thank you,
Mike
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Le Thu, 22 Oct 2015 20:23:24 +0200
"[email protected]" <[email protected]> écrivait:
Quoted 11 lines
Hello I'm trying to understand why and how to add one or more SSD (as a cache drive / keeping xfs log) to a traditional spinning xfs storage volume. I mean: which data will go to the ssd ? Inodes and dentries will go to the ssd ? Will the _read_ performance increase ?
In general I'm looking to increase (cache) the reading performance of folders with a lot of small files (emails), for email servers.
Feel free to let me rtfm :)
I'd gladly study the documentation / articles / benchmarks but my google-fu isn't in best shape.
You've got several options, some integrated with the kernel: dm-cache and bcache, some available as additional tools: flashcache and EnhanceIO.
YMMV, but here's my take:
* flashcache being a facebook internal dev, probably is the most largely deployed one. It's clearly production-ready.
* EnhanceIO works fine but I haven't tested it thoroughly. It adds no signature to the drives so it can be added to existing filesystems (flashcache and bcache need reformatting). However that means that bad thing may happen if you're careless -- it's clearly targeted at always-on servers.
* bcache works fine but the latest fixes haven't been backported, so you should probably use it only with latest (4.2, 4.3) kernels. It's not very mature yet but it's *friggin' fast*.
* dm-cache is the easiest to set-up with the lvmcache command (if your distro is recent enough of course). Like very very easy. It's unfortunately the slowest of the pack, apparently. Doesn't need reformatting IF your existing FS already lives in a LV.
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Emmanuel Florac | Direction technique
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http://oss.sgi.com/mailman/listinfo/xfsQuoted 11 lines · Emmanuel Florac
YMMV, but here's my take:
* flashcache being a facebook internal dev, probably is the most largely deployed one. It's clearly production-ready.
* EnhanceIO works fine but I haven't tested it thoroughly. It adds no signature to the drives so it can be added to existing filesystems (flashcache and bcache need reformatting). However that means that bad thing may happen if you're careless -- it's clearly targeted at always-on servers.
Quoted 8 lines
* bcache works fine but the latest fixes haven't been backported, so you should probably use it only with latest (4.2, 4.3) kernels. It's not very mature yet but it's *friggin' fast*.
* dm-cache is the easiest to set-up with the lvmcache command (if your distro is recent enough of course). Like very very easy. It's unfortunately the slowest of the pack, apparently. Doesn't need reformatting IF your existing FS already lives in a LV.
Very good summary, thanks! Do you also happen to know if all of these retain cache contents across reboots?
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Thank you all for the suggestions!
I'll report back my progress, will take a while .. :)
Bye and have a nice week-end,
Mike
Quoted 16 lines · On Fri, 23 Oct 2015 23:34:00 +0200 Stefan Ring <[email protected]> wrote:
Quoted 15 lines · Emmanuel Florac
YMMV, but here's my take:
* flashcache being a facebook internal dev, probably is the most largely deployed one. It's clearly production-ready.
* EnhanceIO works fine but I haven't tested it thoroughly. It adds no signature to the drives so it can be added to existing filesystems (flashcache and bcache need reformatting). However that means that bad thing may happen if you're careless -- it's clearly targeted at always-on servers.
* bcache works fine but the latest fixes haven't been backported, so you should probably use it only with latest (4.2, 4.3) kernels. It's not very mature yet but it's *friggin' fast*.
Quoted 7 lines
Quoted 4 lines
* dm-cache is the easiest to set-up with the lvmcache command (if your distro is recent enough of course). Like very very easy. It's unfortunately the slowest of the pack, apparently. Doesn't need reformatting IF your existing FS already lives in a LV.
Very good summary, thanks! Do you also happen to know if all of these retain cache contents across reboots?
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Le Fri, 23 Oct 2015 23:34:00 +0200
Stefan Ring <[email protected]> écrivait:
Quoted 2 lines
Very good summary, thanks! Do you also happen to know if all of these retain cache contents across reboots?
Yes, they retain cache contents across reboots.
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Emmanuel Florac | Direction technique
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| +33 1 78 94 84 02
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