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Gankfest
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Joined: 01 Aug 2007
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Location: Miami Beach, FL
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 Posted: Tue Jun 01, 2010 7:22 pm Post subject: Striping size ? |
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What would be the best striping sizes for each partition listed on raid 5:
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/dev/sda1 /boot - 1G Gentoo boot partition ext2
/dev/sda2 / - 250G Gentoo filesystem ext 3, maybe ext4(Not sure which is best)
/dev/sda3 swap - 8G Swap partition for both Gentoo and Debian
/dev/sda4 / - 50G Debian Filesystem ext 3
/dev/sda5 C:/ - 250G Windows 7 Filesystem (Just system files, no downloaded files) NTFS
/dev/sda6 page-file 8G Windows page-file partition(Like Linux swap) NTFS
/dev/sda7 D:/ - About 1.5TB Where all the downloads, movies, music, and games go. This holds really big files and some small files such as pics and mp3's, but majority of the files are over 700MB up too 15GB. NTFS
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Any advice on what the optimal striping sizes should be for each partition listed would be greatly appreciated. This will be my first raid so I'm not quite sure how it works, but thanx in advance for the advice! 
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NeddySeagoon
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Joined: 05 Jul 2003
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| Posted: Tue Jun 01, 2010 8:54 pm Post subject: |
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paradox6996,
Rule 1. /boot must be unraided or raid1 as grub ignores raid and cannot decode raid5, or it chokes at the end of the first stripe on raid0.
Stick with the default stripe sizes then use lvm2 on top of raid5 except for /boot and maybe root. Root on lvm needs an initrd.
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NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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Gankfest
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Joined: 01 Aug 2007
Posts: 946
Location: Miami Beach, FL
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| Posted: Tue Jun 01, 2010 9:11 pm Post subject: |
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| NeddySeagoon wrote: | paradox6996,
Rule 1. /boot must be unraided or raid1 as grub ignores raid and cannot decode raid5, or it chokes at the end of the first stripe on raid0.
Stick with the default stripe sizes then use lvm2 on top of raid5 except for /boot and maybe root. Root on lvm needs an initrd. |
Can a 1G section for the boot be on the same hard-drives as the raid 5, so first partition un-raided for boot then create the raid with the remaining space? Why default size for striping, from what I read it's better to do small striping for small files such as system files, and large stripping for bigger files like games, movies, iso's. If default is the best way to go, then I take your word for it, but would like to know why it's not a good to use custom stripping sizes.
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NeddySeagoon
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| Posted: Wed Jun 02, 2010 6:25 pm Post subject: |
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paradox6996,
You donate partitions to kernel raid sets, not whole drives, so you can mic an match raid levels on the same drive.
I think you can even make a raid5 set on 3 or more partitions on the same drive. You wouldn't want to but you could.
I have four drives partitioned as | Code: | Disk /dev/sda: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0553caf4
Device Boot Start End Blocks Id System
/dev/sda1 * 1 5 40131 fd Linux raid autodetect
/dev/sda2 6 70 522112+ 82 Linux swap / Solaris
/dev/sda4 71 121601 976197757+ 5 Extended
/dev/sda5 71 724 5253223+ fd Linux raid autodetect
/dev/sda6 725 121601 970944471 fd Linux raid autodetect
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sd[abcd]1 is /boot in raid 1
sd[abcd]2 is four swaps - not raided at all, so the kernel will use them as something like raid0
sd[abcd]5 is root in raid5
sd[abcd]6 is the rest of the space, in raid5, then donated to lvm2
This gives me | Code: | $ df -h
Filesystem Size Used Avail Use% Mounted on
rootfs 15G 740M 14G 6% /
/dev/root 15G 740M 14G 6% /
rc-svcdir 1.0M 84K 940K 9% /lib64/rc/init.d
udev 10M 388K 9.7M 4% /dev
shm 4.0G 840K 4.0G 1% /dev/shm
/dev/mapper/vg-home 1008G 610G 348G 64% /home
/dev/mapper/vg-opt 9.9G 902M 8.5G 10% /opt
/dev/mapper/vg-tmp 2.0G 24M 1.9G 2% /tmp
/dev/mapper/vg-var 29G 24G 3.3G 88% /var
/dev/mapper/vg-usr 40G 21G 18G 55% /usr
/dev/mapper/vg-local 1008M 40M 918M 5% /usr/local
/dev/mapper/vg-portage
2.0G 268M 1.6G 15% /usr/portage
/dev/mapper/vg-distfiles
30G 11G 18G 37% /usr/portage/distfiles
/dev/mapper/vg-packages
30G 7.9G 21G 29% /usr/portage/packages
/dev/mapper/vg-vmware
82G 25G 53G 33% /mnt/vmware
/dev/shm 4.0G 0 4.0G 0% /var/tmp/portage
/dev/md1 38M 24M 13M 65% /boot |
I could have combined root and lvm2 and put root inside the lvm2 space but to make that work, you must have an initrd.
What you day about optimising the stripe size to suit the file size is becoming less important with read ahead and large on drive caches.
Also with lvm2, its more difficult to allocate things to physical volumes ... the whole idea is that you don't, so you can grow and shrink 'partitions' on the fly ... no reboot required. Thats worth more to me than the small amount of extra speed from optimising the strip size in the underlying raid.
I do match filesystems to purpose. /dev/mapper/vg-portage and /dev/mapper/vg-tmp are both ext2 with a 1k block size to avoid the wasted space with storing a large number of small files on a filesystem with a 4k block size. Both filesystems are completely expendable, so why have the extra writes associated with a journal?
/dev/mapper/vg-tmp is wiped every boot and /dev/mapper/vg-portage is just the current portage tree.
Hmm ... I suppose I could delete /dev/mapper/vg-tmp and return the space to lvm2 and put /tmp in /dev/shm ... thats in RAM
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NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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Cyker
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