On Mon, 2006-06-05 at 08:00 +0300, Marc A. Volovic wrote: > Quoth Shachar Shemesh: > > > Marc A. Volovic wrote: > > > 2. in case of drive failure, recovery process is a pain > > > > > Well, doing "sfdisk -l /dev/sda > partitions" in advance, and then doing > > "sfdisk /dev/sdb < partitions" isn't all that hard, really. > > Which - especially in the case of complex raid volumes and doubly > especially when also running LVM - makes for managing a whole pile of small > and very important files which tend to *pooof* when the need is greatest.
Create a single partition, mark it as FB, turn on GUID in mkraid, and you're done. I've switched controllers, mixed drive types (SCSI 68/80, IDE/SATA), disconnected IDE drivers by mistake (IDE doe not support hot-plug), killed the kernel, killed the md drivers... I've managed to screw it all, and never saw an MD array die. On the other hand, I've had -very- bad experience with older 3ware (SATA) and Adaptec (SCSI) raid controller. > > > > 3. in case of device move, reintegration of volume is also a pain and may > > > lead to data loss > > > > > Not if you configure MD properly. Properly configured, it finds the > > partitions based on GUID, which means that a move is a no-brainer. > > I have yet to see a case when GUID-based mounting helps rather than > hinders. Especially - again, on post-failure - when re-integrating two > devices with two.... errr... I mixed this up with disk-labels. Doh. Ok, > GUID is possible. But same counter as above - managing GUID labels in a > crisis is error-prone and each mistake increases crisis. Why should -I- manage the GUID by hand? > > > > 4. lower performance than any hardware raid > > > > > ANY hardware raid? > > You obviously have not seen some of the shitty stuff that floats around. > > Yes - ANY hardware raid. and I do NOT mean that crap BIOS-based raids. I > mean normal raids - Mylex, Vortex, Raidcore, LSI, etc. A year ago I compared 3ware 9500 with 6 250GB drives to MD5 raid using two el-cheapo SIL3114 (?) SATA controllers. In most cases, non-static benchmarking (using the in-house data streaming application) showed the 3ware to be ~5-15% faster. In several tests it was actually slower. Upgrading the machine to a faster dual Opteron (instead of the original dual Xeon machine) seem to indicate that the software RAID is scaling better then the hardware one. > > > A RAID controller that will have almost not buffers. > > A controller that will restart resync in the middle if the drive is > > being accessed too much. > > That is flaky or borken (sic) hardware. You call 3ware 8500/9500 flaky? .. I do... but that's me ;) > > > better performer than MD. If you take a GOOD raid controller, MD will > > have poorer performance, but then it's really a question of budget, > > isn't it? > > A raid controller (4 ports, SATA-I) will cost some US$350. Hardly a budget > breaker and well worth it. > > > http://oss.metaparadigm.com/safte-monitor/ > > Ooooh - never saw that. Nice. > > > I do believe you are either biased or always buying from someone else's > > pocket. Either way, all the above do not relate to my situation. > > I am indeed biased and I am not buying from someone elses pocket in all > cases (in many, but not all)... For my personal and professional use, I buy > from my pocket. It is too expensive to buy poor shit or rely on > labour-intensive stuff - my labour (and, in fact, almost everyone's, too) > is too expensive to expend on coddling weird stuff. I do not do system > admin as a hobby, only as a necessary evil. In FC/RHEL you can build the MD array (including the required partition label) from within Anaconda. I doubt that LSI MegaRAID BIOS is easier to operate. > > > On the other hand, it also has some nice things about it, the most > > obvious being that you can use different partitions on the disk at > > different RAID levels. > > Reminds you of my point above on managing little clitical files, no? > Surely, you cavil... > > > As I stated above, it's all a question of budget and trade offs. > > Assume a SATA RAID controller costs US$400. Assume you cost US$80/h (I am > being a cheap bugger). Assume life-cycle at 36 months. The math is NOT > complex. > > My old workspace ate bundles of crap from 3ware... I wouldn't touch a 3ware controller if it was free. Last time I tested LSI's SATA MegaRAID it was dog slow and don't get me started about Adaptec's SATA RAID controller. Gilboa ================================================================= To unsubscribe, send mail to [EMAIL PROTECTED] with the word "unsubscribe" in the message body, e.g., run the command echo unsubscribe | mail [EMAIL PROTECTED]
