wd [and other vendors] sell green drives; they are reasonably cheap but have annoying tendency to spin down very very quickly. i bought recently 2x WD20NPVT-00Z2TT0 with intention of using them [in very unprofessional fashion] in PERC6 RAID1 array.
\n<\/p>\n
those drives park the heads and spin down after 8 seconds of inactivity:<\/p>\n
\r\nwhile [ true ] ; do\r\n sleep 7 ;\r\n smartctl -d sat -a \/dev\/sdb|grep Load_Cycle_Count\r\ndone\r\n<\/pre>\ngives:<\/p>\n
\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 24\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 24\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 24\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 24\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 24\r\n<\/pre>\nwhile the same code with slightly longer sleep value<\/p>\n
\r\nwhile [ true ] ; do\r\n sleep 10 ;\r\n smartctl -d sat -a \/dev\/sdb|grep Load_Cycle_Count\r\ndone\r\n<\/pre>\ngives:<\/p>\n
\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 10\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 11\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 12\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 13\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 14\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 15\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 16\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 16\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 17\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 18\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 19\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 20\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 21\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 22\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 23\r\n<\/pre>\nnotice the increasing value in the last column; such behavior might be fine for a media center machine serving some video from time to time but is undesired for the 24×7 server with some background cron jobs running all the time.<\/p>\n
i have downloaded idle3-tools<\/a> for linux and run <\/p>\n
\r\n.\/idle3ctl -s 129 \/dev\/sdb\r\n<\/pre>\n129 corresponds to idle interval of 30 sec.<\/p>\n
after power off + power on the same test as above gave much better results:<\/p>\n
\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 31\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 31\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 31\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 31\r\n193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 31\r\n<\/pre>\nthe disk is no longer parking after 8s idle period.<\/p>\n
in the long run i’ll use -s 254<\/i> parameter which should correspond to the idle time of 254-128=126 30s periods = 63 min. i’ll add a 30 min cron job dumping smart values to wake the hard drive and monitor of the load cycle count does not increase:<\/p>\n
\r\nsmartctl -d megaraid,2 -a \/dev\/sda >> log\r\nsmartctl -d megaraid,3 -a \/dev\/sda >> log\r\n<\/pre>\nWD20NPVT worked fine in a desktop computer. read and write performance was reasonable – 80-100MB\/s for a sequential access. but then i’ve put the disks to the server. i’ve read earlier that i should expect problems although have not seen any details. i have connected both disks to PERC6 in PE1950 and created RAID1 on 2x WD20NPVT, let it initialize and measured linear access speeds. reads were perfectly fine ~100MB\/s, but writes – never above 30MB\/s. i think i’ve tried it all:<\/p>\n
\n
- creating raid0 on single drive<\/li>\n
- enabling drive’s internal cache [ MegaCli64 -LDSetProp EnDskCache -L1 -a0<\/i> ]<\/li>\n
- checking different stripe size [in theory it should not affect RAID1 as i understand it but apparently it does, although results vary by maybe +\/-10%]<\/li>\n
- turning off and on write-back cache provided by the PERC6<\/li>\n<\/ul>\n
but i never got better write speed. but actually 30MB\/s should be enough for my particular use case. i’ve been running heavy IO load on the server for the last 10 days and so far all works fine.<\/p>\n
i’ll update this post if i encounter any trouble in the future.<\/p>\n
the server which i’m preparing also has 2x WD1000CHTZ wd 1TB raptor drives. there were no performance issues with those. raptors – also in RAID1 – will be boot drives and spool to which rsyncs \/ vmware dumps will arrive. from there rdiff-backup will created copies onto RAID1 on 2x WD20NPVT; from there data will be copied to the offsite location where it’ll be placed on offline media.<\/p>\n
edit<\/b> 2013-07-13 – out of blue write speed deteriorated from tolerable 20MB\/s to 4MB\/s on the 2TB 2.5 green disks. final verdict – don’t mix green WD20NPVT with PERC6. i’m moving data to another machine and will use 2x WD2003FYYS. according to this<\/a> they should work fine with PERC6.
\nedit<\/b> 2014-07-07 – WD RE4 2TB disks work indeed with dell’s PERC6 – they’ve been working flawlessly in RAID1 for the last 12 months under moderate load [ WD2003FYYS, WD2000FYYZ] . WD20NPVT are used as rotated \/ offline backup drives and are doing fine too.<\/p>\n","protected":false},"excerpt":{"rendered":"wd [and other vendors] sell green drives; they are reasonably cheap but have annoying tendency to spin down very very quickly. i bought recently 2x WD20NPVT-00Z2TT0 with intention of using them [in very unprofessional fashion] in PERC6 RAID1 array.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-1668","post","type-post","status-publish","format-standard","hentry","category-tech"],"_links":{"self":[{"href":"https:\/\/kudzia.eu\/b\/wp-json\/wp\/v2\/posts\/1668","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/kudzia.eu\/b\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kudzia.eu\/b\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kudzia.eu\/b\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/kudzia.eu\/b\/wp-json\/wp\/v2\/comments?post=1668"}],"version-history":[{"count":14,"href":"https:\/\/kudzia.eu\/b\/wp-json\/wp\/v2\/posts\/1668\/revisions"}],"predecessor-version":[{"id":2294,"href":"https:\/\/kudzia.eu\/b\/wp-json\/wp\/v2\/posts\/1668\/revisions\/2294"}],"wp:attachment":[{"href":"https:\/\/kudzia.eu\/b\/wp-json\/wp\/v2\/media?parent=1668"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kudzia.eu\/b\/wp-json\/wp\/v2\/categories?post=1668"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kudzia.eu\/b\/wp-json\/wp\/v2\/tags?post=1668"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}