data alignment for SSD: Stripe size or sector size given with -s?
Hi!
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[ANNOUNCE] Btrfs v0.9
[...]
* Stripe size parameter to mkfs.btrfs (-ssize_in_bytes). Extents will be aligned to the stripe size for performance.
[...]
http://fixunix.com/kernel/258991-[announce]-btrfs-v0-9-a.html
versus
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-s, --sectorsize size
Specify the sectorsize, the minimum block allocation.
(man mkfs.btrfs with btrfs-tools 0.19+20101101-1 debian package).
Which one applies? Or do both mention the same? My notion of a sector is something different tough.
I wonder how to set a stripe size for alignment to erase blocks of an Intel SSD 320. Or whether to set anything at all. I want to try to use GPT with ThinkPad T520 UEFI BIOS.
I read from Chris that metadata is basically aligned at 2 MiB already with mount option "ssd" which is default for non rotational media:
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Today, metadata allocations are 4k aligned but we do metadata allocations in cluster of 256k in size (2MB in size in mount -o ssd mode). This results in larger metadata writes, and more contiguous metadata writes. The larger writes give the SSD FTL a better chance of doing more optimal management of the flash.
(Re: SSDs and filesystem alignment... from 2009-02-23,
Message-Id: <[email protected]>)
But what about data alignment?
Ciao,
Signature · 2 lines
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7