Milo if you hunt around you should see papers/articles where it shows foe RAID 5 you need at least 5 drives before you any dramatic performance gains..(sun old Sun articles from around 1998 where they do the math as well).
not sure about RAID 10, but again I *think* you need at least 3 drives in the stripe before you start hitting gains. To best test I'd put ALL the SATA drives into the RAID 5 or RAID 10 array and then see what happens. -- Martin On 1/25/07, Milo Hyson <[EMAIL PROTECTED]> wrote:
I don't really have a whole lot of experience with RAID, so I was wondering if the performance figures I'm seeing are normal or if I just need to tweak things a bit. Based on what I've been reading, I would expect more significant improvements over a single drive. Here's my setup: * FreeBSD 5.4-RELEASE-p22 * AMD Athlon 2200+ * 512 MB RAM * 3ware 9500S-8 RAID controller * 8 x Maxtor 7Y250M0 drives (SATA150 - 250 GB each) * 1 x UDMA100 system drive I'm using a trimmed-down but otherwise stock kernel (see below). The array is configured as two units: a three-drive RAID 5 and a four- drive RAID 10. Both units have been fully initialized and verified. No errors or warnings are being issued by the controller -- everything is green. Using bonnie I get the following results with a 1.5 GB file: -------Sequential Output-------- ---Sequential Input-- --Random-- -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks--- Machine MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec % CPU /sec %CPU single 1536 42229 45.1 44379 19.4 17227 7.7 40819 41.6 44772 12.1 141.1 0.7 raid5 1536 21812 22.8 21876 8.7 12935 5.9 47283 48.3 61998 17.0 152.8 0.8 raid10 1536 21905 23.0 21999 8.6 14878 6.7 49036 50.1 64847 17.7 130.6 0.7 The write times of both RAID configurations are slower than the single drive (which is expected due to having to write to multiple drives). However, I wasn't expecting such a drastic reduction (about 50%). The read times, although faster, are only marginally so in per- char transfer. They're a bit better in block performance, but still not what I would expect. It would seem to me that a read spread across four drives should see more than a 45% performance increase. The highest rate recorded here is only a quarter of the PCI bus- speed, so I doubt that's a bottleneck. CPU load peaks at 50%, so I don't see that being a problem either. I also ran some performance tests with a stock build of PostgreSQL 8.0 to get a different angle on things. Two tests were run on each of the UDMA system drive, the RAID 5 unit, and the RAID 10 unit. The first tested sequential-scans through a 58,000+ record table. The second tested random index-scans of the same table. These were read- only tests -- no write tests were performed. The results are as follows: Unit Seq/sec Index/sec ------------------------------ single 0.550 2048.983 raid5 0.533 2063.900 raid10 0.533 2093.283 Any performance benefit of RAID in these tests is almost nonexistent. Am I doing something wrong? Am I expecting too much? Any advice that can be offered in this area would be much appreciated. Here is my kernel config (the twa driver is loaded as a module): machine i386 cpu I686_CPU ident NAS-20070124 options SCHED_4BSD # 4BSD scheduler options INET # InterNETworking options FFS # Berkeley Fast Filesystem options SOFTUPDATES # Enable FFS soft updates support options UFS_ACL # Support for access control lists options UFS_DIRHASH # Improve performance on big directories options NFSCLIENT # Network Filesystem Client options NFSSERVER # Network Filesystem Server options CD9660 # ISO 9660 Filesystem options PROCFS # Process filesystem (requires PSEUDOFS) options PSEUDOFS # Pseudo-filesystem framework options COMPAT_43 # Compatible with BSD 4.3 [KEEP THIS!] options COMPAT_FREEBSD4 # Compatible with FreeBSD4 options SCSI_DELAY=15000 # Delay (in ms) before probing SCSI options SYSVSHM # SYSV-style shared memory options SYSVMSG # SYSV-style message queues options SYSVSEM # SYSV-style semaphores options _KPOSIX_PRIORITY_SCHEDULING # POSIX P1003_1B real- time extensions options ADAPTIVE_GIANT # Giant mutex is adaptive. device apic # I/O APIC # Bus support. Do not remove isa, even if you have no isa slots device isa device pci # ATA and ATAPI devices device ata device atadisk # ATA disk drives device atapicd # ATAPI CDROM drives options ATA_STATIC_ID # Static device numbering # SCSI support device scbus # SCSI bus (required for SCSI) device da # Direct Access (disks) # atkbdc0 controls both the keyboard and the PS/2 mouse device atkbdc # AT keyboard controller device atkbd # AT keyboard device vga # VGA video card driver # syscons is the default console driver, resembling an SCO console device sc # Floating point support - do not disable. device npx # Serial (COM) ports device sio # 8250, 1650 based serial ports # PCI Ethernet NICs that use the common MII bus controller code. # NOTE: Be sure to keep the 'device miibus' line in order to use these NICs! device miibus # MII bus support device xl # 3com 10/100 # Pseudo devices. device loop # Network loopback device mem # Memory and kernel memory devices device io # I/O device device random # Entropy device device ether # Ethernet support device pty # Pseudo-ttys (telnet etc) -- Milo Hyson CyberLife Labs _______________________________________________ firstname.lastname@example.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to " [EMAIL PROTECTED]"
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